Decoding OBD2 Live Data: A Comprehensive Guide for Automotive Diagnostics

Understanding your vehicle’s health is becoming increasingly accessible thanks to On-Board Diagnostics II (OBD2) systems. One of the most powerful features of OBD2 is its ability to provide live data, offering real-time insights into your car’s engine and various systems as they operate. This stream of information, often referred to as Parameter Identifiers (PIDs), is invaluable for mechanics and car enthusiasts alike in diagnosing issues and monitoring vehicle performance.

This guide delves into the world of OBD2 live data, breaking down common data points and their descriptions to help you understand what your vehicle is telling you. Whether you’re a seasoned technician or just starting to explore automotive diagnostics, understanding these parameters is crucial for effective troubleshooting and maintenance.

Vehicle Operation Parameters

This section covers live data points that reflect the fundamental operation of your vehicle, providing a snapshot of engine performance and driving conditions.

Engine RPM (Revolutions Per Minute)

Engine RPM, or Revolutions Per Minute, is a fundamental parameter that measures how fast your engine’s crankshaft is rotating. It’s a direct indicator of engine speed and is crucial for understanding engine load and performance.

• Normal Range: Varies greatly depending on vehicle and operating conditions. Idle RPM typically ranges from 600-1000 RPM. RPM increases with acceleration and engine load.
• Diagnostic Significance:
  • High RPM at Idle: Could indicate issues like vacuum leaks, throttle body problems, or idle air control valve malfunction.
  • Low RPM or Stalling: May point to fuel delivery problems, ignition issues, or engine sensor failures.
  • Erratic RPM: Suggests misfires, sensor problems, or issues with the engine control system.

Vehicle Speed

Vehicle speed, as the name suggests, reports the current speed of your vehicle. This data point is usually derived from wheel speed sensors and is essential for various vehicle systems, including cruise control, ABS, and traction control.

• Normal Range: Reflects actual driving speed.
• Diagnostic Significance:
  • Speedometer Discrepancy: Comparing live data speed with the speedometer reading can help identify issues with the speedometer itself or wheel speed sensors.
  • ABS/Traction Control Issues: Inconsistencies or missing speed data can trigger ABS or traction control system faults.

Engine Coolant Temperature

Engine Coolant Temperature is a critical parameter indicating the temperature of the engine coolant. Monitored by a coolant temperature sensor, this data is vital for engine management and preventing overheating.

• Normal Range: Typically between 195°F to 220°F (90°C to 105°C) under normal operating conditions, but varies depending on the vehicle and ambient temperature.
• Diagnostic Significance:
  • Overheating (High Temperature): Indicates serious problems like coolant leaks, thermostat failure, radiator issues, or water pump malfunction.
  • Running Cold (Low Temperature): Can be caused by a stuck-open thermostat, leading to reduced fuel efficiency and potentially affecting emissions.
  • Fluctuating Temperature: May suggest air pockets in the cooling system, a failing thermostat, or sensor issues.

Engine Oil Temperature

Engine Oil Temperature measures the temperature of the engine oil. While not as universally reported as coolant temperature, it’s an important parameter for engine lubrication and longevity, especially in high-performance vehicles or under heavy load conditions.

• Normal Range: Typically higher than coolant temperature, often ranging from 210°F to 250°F (99°C to 121°C) under normal operation, but can be higher under strenuous conditions.
• Diagnostic Significance:
  • High Oil Temperature: Indicates excessive engine load, insufficient cooling, or potential lubrication issues. Can lead to oil breakdown and engine damage.
  • Low Oil Temperature: Uncommon, but could suggest sensor malfunction or extremely cold ambient temperatures preventing proper warm-up.

Ambient Air Temperature

Ambient Air Temperature is the temperature of the air outside the vehicle. This reading is used by the engine control unit (ECU) to adjust fuel mixture and ignition timing for optimal performance in varying weather conditions.

• Normal Range: Reflects the actual outside air temperature.
• Diagnostic Significance:
  • Sensor Malfunction: An implausible reading (e.g., extremely high or low when conditions are normal) indicates a faulty ambient air temperature sensor.
  • Climate Control Issues: While primarily for engine management, this sensor can indirectly relate to climate control system performance.

Barometric Pressure

Barometric Pressure, also known as Atmospheric Pressure, is the pressure of the surrounding air. The ECU uses this reading to adjust fuel trim and engine timing, particularly important for vehicles operating at different altitudes.

• Normal Range: Approximately 14.7 PSI (101.3 kPa) at sea level. Decreases with altitude.
• Diagnostic Significance:
  • Sensor Malfunction: Incorrect readings can affect fuel mixture calculations, especially in areas with significant altitude changes.
  • Performance Issues: Inaccurate barometric pressure readings can lead to reduced engine power and fuel efficiency.

Accelerator Pedal Position

Accelerator Pedal Position indicates how far the accelerator pedal is depressed. This is a direct input from the driver and a primary factor in determining engine throttle and vehicle speed.

• Normal Range: 0% (pedal released) to 100% (pedal fully depressed).
• Diagnostic Significance:
  • Throttle Response Issues: Comparing pedal position with throttle position can help diagnose problems in the electronic throttle control system.
  • Cruise Control Problems: Malfunctions in the pedal position sensor can affect cruise control operation.

Relative Accelerator Pedal Position

Relative Accelerator Pedal Position is similar to the absolute position but may be interpreted differently by the vehicle’s computer. It can represent an adjusted or averaged value from multiple sensors, and might not always reach 100% even when the pedal is fully pressed.

• Normal Range: Similar to Accelerator Pedal Position, but may have a slightly different scale or interpretation.
• Diagnostic Significance: Useful in conjunction with Accelerator Pedal Position for detailed analysis of pedal input and sensor behavior.

Commanded Throttle Actuator

Commanded Throttle Actuator represents the throttle position requested by the ECU based on driver input (accelerator pedal position) and other factors. This is the ECU’s target throttle opening.

• Normal Range: 0% (throttle closed) to 100% (throttle fully open).
• Diagnostic Significance:
  • Throttle Control Issues: Comparing commanded throttle position with actual throttle position (see below) is crucial for diagnosing electronic throttle control system problems. Discrepancies indicate issues with the throttle actuator motor, wiring, or ECU control.

Relative Throttle Position

Relative Throttle Position compares the current throttle position to a learned closed position. This parameter accounts for carbon buildup or other factors that can affect throttle plate movement over time.

• Normal Range: 0% (throttle closed relative to learned position) to 100% (throttle fully open).
• Diagnostic Significance:
  • Throttle Body Carbon Buildup: Over time, carbon deposits can accumulate in the throttle body, affecting idle and low-speed performance. Relative throttle position helps the ECU compensate for these changes.
  • Throttle Calibration Issues: Problems with throttle body calibration or sensor drift can be identified by analyzing relative throttle position.

Absolute Throttle Position

Absolute Throttle Position is the actual, physical position of the throttle plate, measured as a percentage of its opening. 0% represents a completely closed throttle, and 100% represents a fully open throttle.

• Normal Range: 0% to 100%.
• Diagnostic Significance:
  • Throttle Sticking or Binding: Inconsistencies between commanded and absolute throttle position can indicate mechanical issues like a sticking throttle plate.
  • Sensor Problems: Faulty throttle position sensors will provide inaccurate absolute throttle position readings.

Control Module Voltage

Control Module Voltage reports the voltage supplied to the engine control unit (ECU). It should be close to the system voltage when the vehicle is running and is distinct from the battery voltage itself.

• Normal Range: Typically around 12-14.5 volts when the engine is running (depending on the charging system).
• Diagnostic Significance:
  • Low Voltage: Indicates potential problems with the charging system (alternator, voltage regulator), battery, or wiring. Low voltage can cause a wide range of ECU malfunctions and sensor errors.
  • High Voltage: Less common, but excessively high voltage can also damage electronic components.

Hybrid Battery Pack Remaining Life

Hybrid Battery Pack Remaining Life (or State of Charge – SOC) shows the percentage of charge remaining in a hybrid vehicle’s battery pack. Standard OBD2 typically provides the overall pack SOC, not individual cell data.

• Normal Range: 0% to 100%. Optimal operating range usually within 20-80% for battery longevity, but varies by vehicle.
• Diagnostic Significance:
  • Low SOC: Expected during normal operation, but excessively low SOC or rapid discharge can indicate battery health issues.
  • Charging System Problems: Failure to maintain SOC can point to problems with the hybrid charging system.

Hybrid/EV Vehicle System Status

This parameter provides status information specific to Hybrid Electric Vehicle (HEV) or Electric Vehicle (EV) systems. It can include:

• HEV Charging State:

  • Charge Sustaining Mode (CSM): The system maintains a constant battery charge level. Common in non-PHEVs.
  • Charge Depletion Mode (CDM): The system allows the battery to discharge, utilizing electric power. Common in PHEVs and EVs.

• HEV Battery Voltage: Voltage of the high-voltage hybrid battery pack (ranges up to 1024V).

• HEV Battery Current: Current flow into or out of the hybrid battery pack. Negative values indicate charging. (Ranges from -3300A to 3300A).

• Diagnostic Significance:

  • Charging System Faults: Abnormal charging states, voltage, or current readings can pinpoint issues within the hybrid/EV charging system.
  • Battery Health Issues: Voltage and current imbalances or deviations from expected values can indicate battery pack problems.

Calculated Engine Load Value

Calculated Engine Load Value is a percentage representing the current airflow into the engine relative to its maximum potential airflow. It’s a measure of how hard the engine is working.

• Normal Range: Varies widely. Low at idle, increases with acceleration and engine load.
• Diagnostic Significance:
  • High Load at Idle: Unexpectedly high load at idle could indicate engine friction, vacuum leaks, or other inefficiencies.
  • Low Load Under Acceleration: May suggest engine performance problems, restricted intake, or sensor issues affecting airflow measurement.

Absolute Load Value

Absolute Load Value is a normalized percentage of air mass per intake stroke, relative to the air mass per intake stroke at 100% throttle. It’s another way to quantify engine load, focusing on air intake.

• Normal Range: Similar to Calculated Engine Load, but may have a slightly different scale.
• Diagnostic Significance: Provides a more direct measure of air intake load and can be useful in diagnosing air intake restrictions or volumetric efficiency problems.

Driver’s Demand Engine – Percent Torque

Driver’s Demand Engine – Percent Torque represents the percentage of maximum engine torque requested by the driver through the accelerator pedal, cruise control, or transmission commands.

• Normal Range: 0% to 100%. Increases with accelerator pedal input.
• Diagnostic Significance:
  • Torque Delivery Issues: Comparing driver’s demand torque with actual engine torque (see below) can reveal discrepancies indicating problems in torque production or delivery.
  • Drive-by-Wire System Problems: Issues within the electronic throttle control system can affect the translation of driver demand into engine torque.

Actual Engine – Percent Torque

Actual Engine – Percent Torque, also known as Indicated Torque, reports the current percentage of the engine’s total available torque. It accounts for net brake torque and friction torque.

• Normal Range: Varies based on engine load and operating conditions.
• Diagnostic Significance:
  • Performance Issues: Low actual torque relative to driver demand can indicate engine performance problems, misfires, fuel delivery issues, or exhaust restrictions.
  • Torque Converter Problems: In automatic transmissions, discrepancies between demanded and actual torque can point to torque converter inefficiencies.

Engine Friction – Percent Torque

Engine Friction – Percent Torque represents the percentage of engine torque consumed by internal engine friction and running engine accessories (water pump, alternator, etc.) under no-load conditions.

• Normal Range: Relatively stable under normal conditions, but can increase with engine wear or accessory drag.
• Diagnostic Significance:
  • Excessive Friction: Increased friction torque can indicate internal engine wear, lubrication problems, or excessive drag from accessories.
  • Engine Efficiency Issues: High friction torque contributes to reduced engine efficiency and fuel economy.

Engine Reference Torque

Engine Reference Torque is a fixed torque rating of the engine, considered 100% for calculating Actual Engine Percentage Torque and other torque-related parameters. This value remains constant and does not change over time.

• Normal Range: A fixed value specific to the engine model.
• Diagnostic Significance: Primarily used as a reference point for other torque-related parameters. Not directly diagnostic on its own, but essential for interpreting percentage torque values.

Engine Percent Torque Data

Engine Percent Torque Data is a parameter used when vehicle conditions can cause the Engine Reference Torque to change dynamically. This is less common than a fixed reference torque.

• Normal Range: Varies depending on vehicle and implementation.
• Diagnostic Significance: Similar to Engine Reference Torque, but indicates a dynamic torque reference that may change based on operating conditions.

Auxiliary Input/Output Status

Auxiliary Input/Output Status is a composite data point that can provide the on/off status of various vehicle systems, including:

• Power Take Off (PTO) and Glow Plug Lamp: Status of PTO systems (used for auxiliary equipment) and diesel glow plugs.

• Automatic Transmission Park/Neutral or Drive/Reverse Status: Gear selector position in automatic transmissions.

• Manual Transmission Neutral/Clutch In or In Gear Status: Gear and clutch status in manual transmissions.

• Recommended Transmission Gear (1 to 15): Suggested gear in vehicles with automated manual or advanced automatic transmissions.

• Diagnostic Significance:

  • Transmission Issues: Incorrect gear status readings can indicate transmission control problems.
  • PTO or Glow Plug System Faults: Status readings can help diagnose issues in auxiliary systems or diesel pre-heating.

Exhaust Gas Temperature (EGT)

Exhaust Gas Temperature (EGT) measures the temperature of exhaust gases at various points in the exhaust system. Sensors are strategically placed to protect components from overheating, particularly in:

• Turbocharger: Crucial for turbocharger health and preventing damage from excessive heat.

• Catalytic Converter: Monitors catalytic converter operating temperature for optimal emissions control and to prevent overheating.

• Diesel Particulate Filter (DPF): Essential for DPF regeneration control and preventing thermal damage.

• NOx Reduction System Components: Monitors temperatures in NOx aftertreatment systems.

• Normal Range: Varies greatly depending on location in the exhaust system and engine load. Turbocharger EGTs can be very high under boost.

• Diagnostic Significance:

  • Overheating Exhaust Components: High EGT readings indicate excessive heat, potentially caused by rich fuel mixtures, restricted exhaust flow, or component malfunctions.
  • Catalytic Converter or DPF Issues: Abnormal EGT readings can be associated with catalytic converter failure, DPF clogging, or regeneration problems.
  • Turbocharger Problems: Excessively high turbo EGTs can lead to turbocharger damage.

Engine Exhaust Flow Rate

Engine Exhaust Flow Rate measures the volume of exhaust gases flowing out of the engine. It’s calculated based on exhaust temperature, volumetric efficiency, engine size, and RPM.

• Normal Range: Varies with engine size, RPM, and load.
• Diagnostic Significance:
  • Exhaust Restrictions: Lower than expected exhaust flow rate can indicate a blockage in the exhaust system (e.g., clogged catalytic converter or muffler).
  • Engine Performance Issues: Abnormal exhaust flow can be related to engine misfires, poor combustion, or volumetric efficiency problems.

Exhaust Pressure

Exhaust Pressure reports the pressure within the exhaust system. It’s displayed as an absolute pressure value when the engine is running and close to ambient atmospheric pressure when the engine is off.

• Normal Range: Slightly above atmospheric pressure when running.
• Diagnostic Significance:
  • Exhaust Restrictions: Elevated exhaust pressure indicates a restriction in the exhaust system.
  • Backpressure Issues: Excessive backpressure can reduce engine performance and fuel efficiency.

Manifold Surface Temperature

Manifold Surface Temperature measures the temperature of the outer surface of the exhaust manifold.

• Normal Range: High temperature when the engine is running, but lower than EGT readings (surface temperature vs. gas temperature).
• Diagnostic Significance:
  • Exhaust System Overheating: Elevated manifold surface temperature can indicate exhaust system issues or potential fire hazards.
  • Catalytic Converter Problems: Excessive heat radiating from the manifold can be related to catalytic converter overheating.

Timing Advance for #1 Cylinder

Timing Advance for #1 Cylinder indicates the ignition timing advance for cylinder #1, measured in degrees relative to Top Dead Center (TDC). Positive values indicate timing advance (spark plug fires before TDC), and negative values indicate timing retard (spark plug fires after TDC).

• Normal Range: Varies depending on engine load, RPM, and operating conditions.
• Diagnostic Significance:
  • Ignition Timing Problems: Incorrect or unstable timing advance can lead to engine misfires, reduced power, and poor fuel economy.
  • Knock Sensor Activity: Excessive timing retard can be a result of knock sensor activity, indicating engine knock or detonation.

Engine Run Time

Engine Run Time provides various parameters related to engine operating time:

• Engine Run Time in Seconds: Total accumulated engine run time.

• Engine Idle Time In Seconds: Total time the engine has spent idling.

• Engine Run Time when PTO is engaged: Run time with Power Take Off engaged (if applicable).

• Diagnostic Significance:

  • Engine Usage Tracking: Total run time is useful for tracking engine usage and maintenance intervals.
  • Excessive Idle Time: High idle time can indicate inefficient vehicle use or potential issues with idle control.

Run Time Since Engine Start

Run Time Since Engine Start measures the elapsed time in seconds since the engine was last started.

• Normal Range: Increases from zero after each engine start.
• Diagnostic Significance: Useful for diagnosing intermittent problems that may occur only after a certain run time.

Time Run with MIL On

Time Run with MIL On (Malfunction Indicator Lamp – Check Engine Light) reports the total engine run time in seconds since the check engine light (MIL) was activated.

• Normal Range: Starts at zero when the MIL is activated and increases as long as the MIL remains on.
• Diagnostic Significance:
  • Tracking MIL Duration: Helps track how long the vehicle has been operated with an active fault code.
  • Intermittent Faults: Can be useful in diagnosing intermittent issues that trigger the MIL sporadically.

Distance Traveled while MIL is Activated

Distance Traveled while MIL is Activated measures the total distance the vehicle has traveled since the check engine light was activated.

• Normal Range: Starts at zero when the MIL is activated and increases with vehicle mileage.
• Diagnostic Significance: Similar to Time Run with MIL On, providing a mileage-based perspective on operating with a fault.

Time since Trouble Codes Cleared

Time since Trouble Codes Cleared reports the total engine run time in seconds since diagnostic trouble codes (DTCs) were last cleared (either by a scan tool or battery disconnection).

• Normal Range: Starts at zero after code clearing and increases with engine run time.
• Diagnostic Significance:
  • Post-Repair Monitoring: Helps monitor if fault codes reappear after repairs have been made.
  • Identifying Recurring Issues: Short time since code clearing before codes reappear indicates a persistent or recurring problem.

Distance Traveled Since Codes Cleared

Distance Traveled Since Codes Cleared measures the total distance traveled since diagnostic trouble codes were last cleared.

• Normal Range: Starts at zero after code clearing and increases with vehicle mileage.
• Diagnostic Significance: Similar to Time since Trouble Codes Cleared, but mileage-based.

Warm-ups Since Codes Cleared

Warm-ups Since Codes Cleared counts the number of engine warm-up cycles that have occurred since codes were last cleared. A warm-up cycle is defined as the coolant temperature reaching at least 40°F after startup and then reaching at least 170°F.

• Normal Range: Increments with each engine warm-up cycle after code clearing.
• Diagnostic Significance:
  • Monitoring Readiness Tests: Emission readiness monitors often require a certain number of warm-up cycles to complete after codes are cleared.
  • Intermittent Faults: The number of warm-ups before codes reappear can provide clues about the nature of intermittent problems.

Fuel & Air Parameters

This section focuses on live data related to the fuel and air systems, crucial for engine combustion and efficiency.

Fuel System Status

Fuel System Status indicates the operating mode of the fuel system, typically showing whether it’s in Open Loop or Closed Loop mode.

• Open Loop Mode: The ECU uses pre-programmed air-fuel ratios and ignores feedback from the oxygen sensors. This mode is often used during engine warm-up or under heavy load.

• Closed Loop Mode: The ECU uses feedback from the oxygen sensors to adjust the air-fuel ratio in real-time, aiming for the optimal stoichiometric ratio for emissions control and fuel efficiency.

• Diagnostic Significance:

  • Stuck in Open Loop: If the fuel system remains in open loop mode after warm-up, it can indicate problems with oxygen sensors, coolant temperature sensor, or other sensor inputs that prevent closed-loop operation.
  • Fuel Trim Issues: Understanding the fuel system status is important when interpreting fuel trim data (see below).

Oxygen Sensor Voltage

Oxygen Sensor Voltage measures the voltage output of the oxygen sensors (O2 sensors) in the exhaust system. These sensors monitor the oxygen content in the exhaust gas and provide feedback to the ECU for fuel mixture adjustments in closed loop mode.

• Normal Range: Typically fluctuates between 0.1V and 0.9V in closed loop operation.

  • Low Voltage (around 0.1V): Indicates a lean mixture (excess oxygen).
  • High Voltage (around 0.9V): Indicates a rich mixture (low oxygen).
  • Voltage Stuck High or Low: Suggests a faulty oxygen sensor.

• Diagnostic Significance:

  • Fuel Mixture Problems: Abnormal oxygen sensor voltage readings are a primary indicator of rich or lean fuel mixture conditions.
  • Sensor Failure: A sensor that is stuck at a fixed voltage or shows no fluctuation is likely faulty.

Oxygen Sensor Equivalence Ratio (Lambda)

Oxygen Sensor Equivalence Ratio, also known as Lambda, is another way to represent the air-fuel mixture based on oxygen sensor readings. It’s the ratio of the actual air-fuel ratio to the ideal stoichiometric air-fuel ratio (14.7:1 for gasoline).

• Normal Range: Ideally, Lambda should oscillate around 1.0 in closed loop mode.

  • Lambda > 1.0: Lean mixture.
  • Lambda < 1.0: Rich mixture.
  • Lambda = 1.0: Stoichiometric mixture (ideal).

• Diagnostic Significance: Similar to Oxygen Sensor Voltage, Lambda provides information about air-fuel mixture and oxygen sensor function.

Oxygen Sensor Current

Oxygen Sensor Current is the current flowing through certain types of oxygen sensors (typically wideband or air-fuel ratio sensors). This current is directly related to the air-fuel ratio.

• Normal Range: Around 0 mA for a stoichiometric mixture.

  • Positive Current: Lean mixture (excess air).
  • Negative Current: Rich mixture (excess fuel).

• Diagnostic Significance: Provides a more precise measure of air-fuel ratio compared to voltage-based oxygen sensors, especially in wideband sensors.

Short Term Fuel Trim (STFT)

Short Term Fuel Trim (STFT) represents the immediate, real-time adjustments the ECU is making to the fuel mixture in response to oxygen sensor feedback. It’s a percentage adjustment to the base fuel delivery.

• Normal Range: Ideally, STFT should be close to 0%, fluctuating slightly around this value in closed loop operation. Small deviations (e.g., ±10%) are usually acceptable.

  • Positive STFT: The ECU is adding fuel to compensate for a lean condition (too much air).
  • Negative STFT: The ECU is removing fuel to compensate for a rich condition (too much fuel).

• Diagnostic Significance:

  • Lean or Rich Conditions: Consistently positive or negative STFT values indicate a lean or rich running condition, respectively.
  • Vacuum Leaks (Lean): Vacuum leaks often cause positive STFT as the ECU tries to compensate for unmetered air entering the engine.
  • Fuel Injector Issues (Rich or Lean): Faulty or clogged fuel injectors can cause rich or lean conditions, reflected in STFT.

Long Term Fuel Trim (LTFT)

Long Term Fuel Trim (LTFT) represents learned fuel mixture adjustments that the ECU stores over time to compensate for long-term changes in engine or sensor characteristics. It’s a more persistent adjustment than STFT.

• Normal Range: Ideally, LTFT should be close to 0%. Small deviations (e.g., ±10%) are generally acceptable.

  • Positive LTFT: The ECU has consistently added fuel over time to compensate for a lean condition.
  • Negative LTFT: The ECU has consistently removed fuel over time to compensate for a rich condition.

• Diagnostic Significance:

  • Long-Term Fuel Mixture Problems: Significantly positive or negative LTFT values indicate a persistent lean or rich running condition that the ECU is trying to correct.
  • Systematic Issues: LTFT values can help identify systematic problems like fuel pressure issues, MAF sensor drift, or persistent vacuum leaks.
  • Fuel Injector Degradation: Over time, fuel injectors can become clogged or have reduced flow, leading to lean conditions and positive LTFT.

Commanded Equivalence Ratio (CER)

Commanded Equivalence Ratio (CER), also known as Commanded Lambda, is the target air-fuel ratio (expressed as Lambda) that the ECU is commanding the engine to achieve.

• Normal Range:

  • Wide Range O2 Sensors: CER is displayed in both open and closed loop modes.
  • Conventional O2 Sensors: CER is displayed in open loop mode. In closed loop mode, it typically reads 1.0 (stoichiometric).

• Diagnostic Significance: Shows the ECU’s intended air-fuel ratio target. Comparing CER with actual oxygen sensor readings can help diagnose control system issues.

Mass Air Flow Rate (MAF)

Mass Air Flow Rate (MAF) measures the amount of air entering the engine, typically in grams per second (g/s). The MAF sensor is crucial for accurate fuel delivery calculations.

• Normal Range: Varies with engine size and RPM.

  • Idle: 2-7 g/s (typical range).
  • 2500 RPM: 15-25 g/s (typical range).
  • Refer to manufacturer specifications for precise values.

• Diagnostic Significance:

  • MAF Sensor Malfunction: Incorrect MAF readings can cause lean or rich conditions, driveability problems, and fault codes.
  • Air Intake Restrictions: Lower than expected MAF readings can indicate a blockage in the air intake system (e.g., clogged air filter).
  • Vacuum Leaks: Vacuum leaks downstream of the MAF sensor can cause inaccurate readings and lean conditions.

Intake Air Temperature (IAT)

Intake Air Temperature (IAT) measures the temperature of the air entering the engine’s intake manifold. This sensor helps the ECU adjust fuel mixture and ignition timing based on air density.

• Normal Range: Should generally reflect ambient air temperature, but can be higher due to engine heat soak.
• Diagnostic Significance:
  • IAT Sensor Malfunction: Incorrect IAT readings can affect fuel mixture calculations and performance.
  • Heat Soak Issues: Excessively high IAT readings can indicate poor air intake design or heat soak problems, potentially reducing engine power.

Intake Manifold Absolute Pressure (MAP)

Intake Manifold Absolute Pressure (MAP) measures the absolute pressure within the intake manifold. It’s used by the ECU to determine engine load and air density, especially in naturally aspirated engines.

• Normal Range:

  • Running Engine: 18-20 “Hg vacuum (inches of mercury). Lower absolute pressure.
  • Idle Engine: 18-20 “Hg vacuum.
  • Wide Open Throttle (WOT): Pressure approaches atmospheric pressure (vacuum approaches 0 “Hg).

• Diagnostic Significance:

  • Vacuum Leaks: Higher than expected MAP readings (less vacuum) at idle indicate vacuum leaks.
  • MAP Sensor Malfunction: Incorrect MAP readings can cause fuel mixture problems and performance issues.
  • Boost Pressure (Turbo/Supercharged Engines): In forced induction engines, MAP sensor readings will be above atmospheric pressure under boost.

Fuel Pressure (Gauge)

Fuel Pressure (Gauge) reports the fuel pressure in the fuel system, measured relative to atmospheric pressure (gauge pressure). A reading of 0 psi indicates atmospheric pressure.

• Normal Range: Varies significantly depending on the fuel system type and vehicle (e.g., port fuel injection vs. direct injection). Refer to manufacturer specifications.
• Diagnostic Significance:
  • Low Fuel Pressure: Indicates fuel pump problems, fuel filter blockage, fuel pressure regulator issues, or fuel leaks. Can cause lean running, misfires, and stalling.
  • High Fuel Pressure: May be caused by a faulty fuel pressure regulator or return line blockage. Can cause rich running and fuel leaks.

Fuel Rail Pressure

Fuel Rail Pressure is similar to Fuel Pressure (Gauge), reporting the fuel pressure in the fuel rail as a gauge pressure.

• Normal Range: Same as Fuel Pressure (Gauge), varies by vehicle.
• Diagnostic Significance: Same as Fuel Pressure (Gauge).

Fuel Rail Pressure (Absolute)

Fuel Rail Pressure (Absolute) reports the fuel pressure in the fuel rail as an absolute pressure, meaning it’s referenced to a perfect vacuum (not atmospheric pressure). When the fuel rail is not pressurized, it will read approximately atmospheric pressure (14.7 psi or 101.3 kPa).

• Normal Range: Absolute fuel pressure values will be higher than gauge pressure values by approximately atmospheric pressure.
• Diagnostic Significance: Provides a more fundamental measure of fuel pressure compared to gauge pressure.

Fuel Rail Pressure (relative to manifold vacuum)

Fuel Rail Pressure (relative to manifold vacuum) reports the fuel pressure in the fuel rail relative to the vacuum pressure in the intake manifold. This is relevant in some fuel systems where fuel pressure is regulated based on manifold vacuum.

• Normal Range: Varies depending on the fuel system and manifold vacuum.
• Diagnostic Significance: Useful for diagnosing fuel pressure regulation issues in vacuum-referenced fuel systems.

Alcohol Fuel %

Alcohol Fuel % reports the percentage of ethanol or alcohol content in the fuel, as measured by the engine computer. For example, E85 fuel would show approximately 85%.

• Normal Range: 0% for gasoline without ethanol, up to 85% or higher for flex-fuel vehicles using ethanol blends.
• Diagnostic Significance:
  • Flex-Fuel Sensor Issues: Incorrect alcohol fuel percentage readings can indicate problems with the flex-fuel sensor, potentially affecting fuel mixture calculations.
  • Fuel Quality Concerns: Unexpected alcohol content readings may suggest fuel quality issues.

Fuel Level Input

Fuel Level Input reports the percentage of fuel remaining in the fuel tank, based on the fuel level sensor.

• Normal Range: 0% (empty) to 100% (full).
• Diagnostic Significance:
  • Fuel Gauge Problems: Discrepancies between live data fuel level and the fuel gauge reading can indicate issues with the fuel gauge or fuel level sensor.
  • Fuel Consumption Monitoring: Can be used to track fuel consumption over time.

Engine Fuel Rate

Engine Fuel Rate reports the near-instantaneous fuel consumption rate, typically in Liters or Gallons per hour. It’s calculated by the ECU based on fuel injection parameters.

• Normal Range: Varies significantly depending on engine size, load, and RPM. Low at idle, increases with acceleration.
• Diagnostic Significance:
  • Fuel Efficiency Monitoring: Provides real-time fuel consumption data.
  • Fuel System Problems: Abnormal fuel consumption rates can indicate fuel leaks, inefficient engine operation, or fuel system issues.

Cylinder Fuel Rate

Cylinder Fuel Rate reports the calculated amount of fuel injected per cylinder during the most recent intake stroke, typically in milligrams per stroke (mg/stroke).

• Normal Range: Varies depending on engine load and operating conditions.
• Diagnostic Significance:
  • Cylinder Imbalance: Significant variations in cylinder fuel rates can indicate fuel injector problems or cylinder-specific issues (e.g., compression problems).
  • Fuel Injector Performance: Can help assess individual fuel injector performance and identify clogged or leaking injectors.

Fuel System Percentage Use

Fuel System Percentage Use reports the percentage of total fuel usage for each cylinder bank (up to four banks). This can be used to monitor fuel distribution in multi-bank engines or vehicles with multiple fuel systems (e.g., diesel and CNG).

• Normal Range: Should be relatively balanced across banks in most cases.
• Diagnostic Significance:
  • Fuel Distribution Issues: Significant imbalances in fuel usage between banks can indicate fuel delivery problems to specific cylinder banks.
  • Multi-Fuel System Monitoring: Useful for monitoring fuel usage in vehicles with multiple fuel systems.

Fuel Injection Timing

Fuel Injection Timing reports the angle of crankshaft rotation before Top Dead Center (BTDC) at which fuel injection begins. Positive angles indicate injection before TDC, and negative angles indicate injection after TDC.

• Normal Range: Varies depending on engine type, load, and operating conditions.
• Diagnostic Significance:
  • Injection Timing Problems: Incorrect or erratic injection timing can lead to poor combustion, reduced power, and increased emissions.
  • Engine Control Issues: Problems with ECU control of injection timing can be identified.

Fuel System Control

Fuel System Control provides status information for various aspects of the fuel system in diesel vehicles, including:

• Fuel Pressure Control: Open or closed loop control status.
• Fuel Injection Quantity: Open or closed loop control status.
• Fuel Injection Timing: Open or closed loop control status.
• Idle Fuel Balance/Contribution: Open or closed loop control status.

Closed loop control indicates the system is using sensor feedback for fine-tuning.

• Diagnostic Significance: Helps understand the control strategy and identify issues within the diesel fuel system control loops.

Fuel Pressure Control System

Fuel Pressure Control System provides detailed data for up to two fuel rails, including:

• Commanded Rail Pressure: Target fuel rail pressure set by the ECU.
• Actual Rail Pressure: Measured fuel rail pressure.
• Temperature: Fuel temperature in the rail.

Pressure is reported as gauge pressure.

• Diagnostic Significance:
  • Fuel Pressure Regulation Issues: Discrepancies between commanded and actual rail pressure indicate problems with fuel pressure regulation (e.g., fuel pressure regulator, pump control).
  • Fuel Temperature Problems: Excessively high fuel temperature can affect fuel density and performance.

Injection Pressure Control System

Injection Pressure Control System is relevant for some diesel engines that use a high-pressure oil system to control fuel injection pressure (Hydraulic Electronic Unit Injection – HEUI). Parameters include:

• Commanded Control Pressure Rail A/B: Target oil pressure for injection control.

• Actual Pressure Rail A/B: Measured oil pressure for injection control.

• Diagnostic Significance:

  • HEUI System Problems: Abnormal oil pressure readings in the HEUI system can indicate issues with the high-pressure oil pump, injectors, or control system.

Boost Pressure Control

Boost Pressure Control provides data related to turbocharger boost pressure, including:

• ECM Commanded Boost Pressure: Target boost pressure set by the ECU.
• Actual Boost Pressure: Measured boost pressure.

All data is reported as absolute pressure. To convert to gauge pressure (boost as commonly referred to), subtract atmospheric pressure (approximately 14.7 psi).

• Diagnostic Significance:
  • Boost Leaks: Lower than expected actual boost pressure compared to commanded boost indicates boost leaks in the intake system.
  • Turbocharger Problems: Inability to reach commanded boost levels can suggest turbocharger issues, wastegate problems, or boost control solenoid malfunctions.
  • Overboost Conditions: Excessively high boost pressure can be caused by wastegate failures or boost control problems.

Turbocharger RPM

Turbocharger RPM measures the rotational speed of the turbocharger turbine, typically in revolutions per minute (RPM).

• Normal Range: Varies greatly depending on engine load and boost demand. Can reach very high RPMs (hundreds of thousands).
• Diagnostic Significance:
  • Turbocharger Failure: Zero or abnormally low turbo RPM indicates turbocharger failure or lack of turbocharger operation.
  • Turbo Lag: Slow turbo RPM response can contribute to turbo lag.
  • Over-Speeding: Excessively high turbo RPM can indicate potential turbocharger stress or damage.

Turbocharger Temperature

Turbocharger Temperature provides temperature readings at various points in the turbocharger system:

• Compressor Inlet Temperature: Air temperature before the turbo compressor.

• Compressor Outlet Temperature: Air temperature after the turbo compressor (should be significantly higher due to compression).

• Turbine Inlet Temperature: Exhaust gas temperature entering the turbine (pre-turbo EGT).

• Turbine Outlet Temperature: Exhaust gas temperature exiting the turbine (post-turbo EGT).

• Normal Range: Compressor outlet temperatures should be higher than inlet temperatures. Turbine inlet temperatures are typically much higher than compressor temperatures.

• Diagnostic Significance:

  • Intercooler Inefficiency: High compressor outlet temperatures can indicate intercooler inefficiency or problems.
  • Turbocharger Overheating: Excessively high turbine inlet temperatures can damage the turbocharger.
  • Charge Air Leaks: Temperature discrepancies can help identify charge air leaks.

Turbocharger Compressor Inlet Pressure Sensor

Turbocharger Compressor Inlet Pressure Sensor measures the pressure at the turbocharger inlet, reported as absolute pressure. Should be close to atmospheric pressure under normal conditions.

• Normal Range: Approximately 14.7 psi (101.3 kPa) or slightly below, reflecting atmospheric pressure.
• Diagnostic Significance:
  • Air Intake Restrictions: Lower than atmospheric pressure at the turbo inlet can indicate air intake restrictions upstream of the turbocharger.
  • Sensor Malfunction: Incorrect pressure readings can indicate a faulty sensor.

Variable Geometry Turbo (VGT) Control

Variable Geometry Turbo (VGT) Control provides data related to the position of the vanes in variable geometry turbochargers, which are used to optimize turbo performance across different engine speeds and loads.

• Commanded VGT Position: Target vane position requested by the ECU (0% – maximum bypass, 100% – maximum boost).

• Actual VGT Vane Position: Measured vane position.

• VGT Control Status: Open Loop, Closed Loop, or Fault State.

• Normal Range: VGT position varies dynamically based on engine load and RPM.

• Diagnostic Significance:

  • VGT Actuator Problems: Discrepancies between commanded and actual VGT position indicate issues with the VGT actuator motor, linkage, or control system.
  • Stuck VGT Vanes: VGT vanes that are stuck or binding can cause performance problems and fault codes.

Wastegate Control

Wastegate Control provides data related to the wastegate in turbocharged engines, which is used to regulate boost pressure by bypassing exhaust gas around the turbine.

• Commanded Wastegate Position: Target wastegate position requested by the ECU (0% – fully closed, 100% – fully open).

• Actual Wastegate Position: Measured wastegate position.

• Normal Range: Wastegate position varies dynamically based on boost pressure control.

• Diagnostic Significance:

  • Wastegate Actuator Problems: Discrepancies between commanded and actual wastegate position indicate issues with the wastegate actuator, linkage, or control system.
  • Stuck Wastegate: A stuck-closed wastegate can lead to overboost conditions. A stuck-open wastegate can cause underboost.

Charge Air Cooler Temperature (CACT)

Charge Air Cooler Temperature (CACT) measures the temperature of the charge air after it has passed through the intercooler (charge air cooler) in turbocharged vehicles. May have multiple sensors (Bank 1 Sensor 1, Bank 1 Sensor 2, Bank 2 Sensor 1, Bank 2 Sensor 2).

• Normal Range: CACT should be significantly lower than compressor outlet temperature, indicating effective intercooler operation.
• Diagnostic Significance:
  • Intercooler Inefficiency: High CACT readings indicate intercooler inefficiency, potentially due to blockage, damage, or airflow restrictions.
  • Charge Air Leaks: Temperature discrepancies between sensors can help identify charge air leaks in the intercooler system.

Emissions Control Parameters

This section covers live data points related to vehicle emissions control systems, essential for meeting emission standards and diagnosing emission-related faults.

Commanded EGR

Commanded EGR (Exhaust Gas Recirculation) represents the target opening percentage of the EGR valve, as requested by the ECU. EGR valves recirculate a portion of exhaust gas back into the intake manifold to reduce NOx emissions.

• Normal Range: 0% (fully closed) to 100% (fully open). EGR valve opening varies based on engine load and operating conditions.
• Diagnostic Significance:
  • EGR System Problems: Comparing commanded EGR with EGR Error (see below) can help diagnose issues with the EGR valve, actuator, or control system.

EGR Error

EGR Error reports the percentage difference between the commanded EGR opening and the actual EGR valve opening.

• Normal Range: Ideally, EGR Error should be close to 0%.
• Diagnostic Significance:
  • EGR Valve Malfunction: Significant EGR Error indicates that the EGR valve is not responding correctly to ECU commands, potentially due to valve sticking, actuator problems, or sensor issues.

Commanded Diesel Intake Air Flow Control

Commanded Diesel Intake Air Flow Control, also known as EGR Throttle, is used in some newer diesel engines to create intake vacuum for EGR flow control.

• Commanded Position: Target position of the EGR throttle plate (0% – closed to 100% – open).
• Actual Position: Measured position of the EGR throttle plate.

May have primary and secondary EGR throttles.

• Diagnostic Significance:
  • EGR Throttle Problems: Discrepancies between commanded and actual EGR throttle position indicate issues with the EGR throttle actuator or control system.

Exhaust Gas Recirculation Temperature

Exhaust Gas Recirculation Temperature (EGRT) measures the temperature of the recirculated exhaust gas at various points in the EGR system. May have multiple sensors (EGRTA – Bank 1 Pre-Cooler, EGRTB – Bank 1 Post-Cooler, EGRTC – Bank 2 Pre-Cooler, EGRTD – Bank 2 Post-Cooler).

• Normal Range: EGRT should be lower than exhaust manifold temperature, but higher than intake air temperature. Post-cooler temperatures should be lower than pre-cooler temperatures if EGR cooler is present.
• Diagnostic Significance:
  • EGR Cooler Problems: Abnormal EGRT readings, especially post-cooler temperatures, can indicate EGR cooler malfunction or blockage.
  • EGR Flow Issues: Temperature discrepancies can help diagnose EGR flow problems.

EVAP System Vapor Pressure

EVAP System Vapor Pressure measures the gauge pressure within the Evaporative Emission Control System (EVAP system), which prevents fuel vapors from escaping into the atmosphere.

• Normal Range: Typically a slight vacuum or slight positive pressure, depending on system operation.
• Diagnostic Significance:
  • EVAP System Leaks: Inability to maintain vacuum or pressure in the EVAP system indicates leaks in hoses, seals, or components.
  • EVAP Purge Valve Problems: Malfunctioning purge valves can cause abnormal EVAP system pressure readings.

Absolute Evap System Vapor Pressure

Absolute Evap System Vapor Pressure is similar to EVAP System Vapor Pressure, but reported as absolute pressure.

• Normal Range: Absolute EVAP pressure values will be higher than gauge pressure values by approximately atmospheric pressure.
• Diagnostic Significance: Same as EVAP System Vapor Pressure.

Commanded Evaporative Purge

Commanded Evaporative Purge represents the target purge flow rate of the EVAP system, as requested by the ECU. The purge valve controls the flow of fuel vapors from the EVAP canister into the intake manifold for combustion.

• Normal Range: 0% (purge valve closed) to 100% (purge valve fully open). Purge flow typically occurs under certain engine operating conditions.
• Diagnostic Significance:
  • EVAP Purge Valve Problems: Comparing commanded purge with EVAP system pressure readings can help diagnose purge valve malfunctions.

Catalyst Temperature

Catalyst Temperature measures the temperature of the catalytic converter. May have multiple sensors (Bank 1 Sensor 1 – pre-cat, Bank 1 Sensor 2 – post-cat, etc.).

• Normal Range: Catalytic converter temperature typically rises significantly after engine warm-up and under load.
• Diagnostic Significance:
  • Catalytic Converter Overheating: Excessively high catalyst temperatures can damage the catalytic converter.
  • Catalytic Converter Inefficiency: Low catalyst temperatures can indicate that the catalytic converter is not functioning effectively.
  • Exhaust System Problems: Abnormal catalyst temperatures can be related to rich fuel mixtures, misfires, or exhaust restrictions.

Diesel Aftertreatment Status

Diesel Aftertreatment Status provides a composite data point reporting the status of various diesel aftertreatment systems, including Diesel Particulate Filter (DPF) and NOx Adsorber systems. May include:

• DPF Regeneration Status: Active/Not Active.

• DPF Regeneration Type: Passive/Active/Forced.

• NOx Absorber Regen Status: Active/Not Active.

• NOx Absorber Desulfurization Status: Active/Not Active.

• Normalized Trigger for DPF Regen: Percentage until next regen event.

• Average Time Between DPF Regens: Average time between DPF regenerations.

• Average Distance Between DPF Regens: Average distance between DPF regenerations.

• Diagnostic Significance:

  • DPF Clogging: Regeneration status, trigger percentage, and average regen intervals provide insights into DPF health and clogging.
  • NOx System Problems: NOx absorber regeneration and desulfurization status can help diagnose NOx aftertreatment issues.

Diesel Exhaust Fluid Sensor Data

Diesel Exhaust Fluid (DEF) Sensor Data provides information related to the DEF system in diesel vehicles using Selective Catalytic Reduction (SCR) for NOx reduction. May include:

• DEF Type: DEF fluid type identification (Urea too high/low, Proper DEF, Sensor fault).

• DEF Concentration: Urea concentration in DEF fluid (should be around 32.5% for proper DEF).

• DEF Tank Temperature: DEF tank temperature.

• DEF Tank Level: DEF tank level percentage.

• Diagnostic Significance:

  • DEF Quality Issues: DEF type and concentration readings can identify problems with DEF fluid quality or contamination.
  • DEF System Malfunctions: Tank level and temperature readings can help diagnose DEF system sensor or component failures.

Diesel Particulate Filter (DPF)

Diesel Particulate Filter (DPF) parameters provide pressure readings related to the DPF:

• Inlet Pressure: Pressure before the DPF.
• Outlet Pressure: Pressure after the DPF.
• Differential Pressure: Pressure difference across the DPF (Inlet Pressure – Outlet Pressure).

May have sensors for Bank 1 and Bank 2.

• Normal Range: Differential pressure should be low under normal DPF operation.
• Diagnostic Significance:
  • DPF Clogging: Increased differential pressure indicates soot accumulation and DPF clogging.
  • DPF Blockage: High differential pressure can also indicate a DPF blockage or failure.

Diesel Particulate Filter (DPF) Temperature

Diesel Particulate Filter (DPF) Temperature reports temperature readings related to the DPF:

• Inlet Temperature: Temperature of exhaust gas entering the DPF.
• Outlet Temperature: Temperature of exhaust gas exiting the DPF.

May have sensors for Bank 1 and Bank 2.

• Normal Range: DPF temperatures increase during regeneration.
• Diagnostic Significance:
  • DPF Regeneration Monitoring: DPF temperature readings are crucial for monitoring DPF regeneration and ensuring proper operation.
  • DPF Overheating: Excessively high DPF temperatures can damage the DPF.

NOx Sensor

NOx Sensor data reports the concentration of Nitrogen Oxides (NOx) in the exhaust gas, measured in parts per million (ppm). May have multiple sensors (Bank 1 Sensor 1 – pre-NOx adsorber, Bank 1 Sensor 2 – post-NOx adsorber, etc.).

• Normal Range: NOx levels should be reduced after passing through NOx aftertreatment systems.
• Diagnostic Significance:
  • NOx Aftertreatment Inefficiency: High NOx readings after the NOx aftertreatment system indicate system inefficiency or failure.
  • NOx Sensor Malfunction: Incorrect NOx readings can indicate a faulty NOx sensor.

NOx Control System

NOx Control System provides data related to the Selective Catalytic Reduction (SCR) or NOx Adsorber system:

• Average Reagent Consumption Rate: Average DEF or reagent consumption rate.

• Average Demanded Consumption Rate: Target reagent consumption rate commanded by the ECU.

• Reagent Tank Level: DEF or reagent tank level percentage.

• NOx Warning Indicator Time: Time since NOx warning light activation.

• Diagnostic Significance:

  • DEF System Problems: Reagent consumption rate, tank level, and warning indicator time help diagnose DEF system issues.
  • SCR System Inefficiency: Discrepancies between demanded and actual reagent consumption can indicate SCR system problems.

NOx Sensor Corrected Data

NOx Sensor Corrected Data reports NOx concentration readings that have been corrected by the ECU, including learned adjustments and offsets.

• Normal Range: Similar to NOx Sensor data, but may be more accurate due to ECU corrections.
• Diagnostic Significance: Provides a more refined NOx reading for diagnostic purposes.

NOx NTE Control Area Status

NOx NTE (Not-To-Exceed) Control Area Status indicates whether the vehicle is operating within the NOx NTE control area, which is a defined engine operating range for emissions testing. Also reports on manufacturer exemptions and NTE-related deficiencies.

• Status Indicators:

  • Inside/Outside NOx Control Area.
  • Inside/Outside Manufacturer Exception Area.
  • NTE Related Deficiency Present.

• Diagnostic Significance: Primarily relevant for emissions compliance testing and diagnostics related to NTE regulations.

PM Sensor Bank 1 & 2

PM Sensor Bank 1 & 2 data provides status information for Particulate Matter (PM) sensors:

• Particulate matter sensor active: Yes/No.

• Particulate matter sensor regenerating: Yes/No.

• Particulate matter sensor value: PM accumulation level (0% – clean, 100% – regen required).

• Diagnostic Significance:

  • PM Sensor Health: Sensor active and regenerating status indicates sensor functionality.
  • Particulate Matter Accumulation: Sensor value provides an indication of PM buildup in the exhaust system.

Particulate Matter (PM) Sensor

Particulate Matter (PM) Sensor reports the soot concentration in the exhaust gas, measured in mg/m3. May have sensors for Bank 1 and Bank 2.

• Normal Range: PM concentration should be low after passing through a DPF.
• Diagnostic Significance:
  • DPF Efficiency: High PM readings after the DPF indicate DPF inefficiency or failure.
  • PM Sensor Malfunction: Incorrect PM readings can indicate a faulty PM sensor.

PM NTE Control Area Status

PM NTE Control Area Status is similar to NOx NTE Control Area Status, but for Particulate Matter emissions. Indicates whether the vehicle is operating within the PM NTE control area and reports on manufacturer exemptions and NTE-related deficiencies.

• Status Indicators:

  • Inside/Outside PM Control Area.
  • Inside/Outside Manufacturer Exception Area.
  • NTE Related Deficiency Present.

• Diagnostic Significance: Primarily relevant for emissions compliance testing and diagnostics related to PM NTE regulations.

SCR Inducement System

SCR Inducement System reports the status of the inducement system in Selective Catalytic Reduction (SCR) systems. Inducement strategies are used to alert drivers to SCR system issues and may include warnings or vehicle performance limitations.

• SCR Inducement Status: On/Off.

• Reasons for Activation: Low reagent level, incorrect reagent, abnormal consumption, excessive NOx.

• Historical Inducement Data: Inducement status and distance traveled in 10,000 km intervals.

• Diagnostic Significance:

  • DEF System Issues: Inducement status and reasons for activation help diagnose DEF system problems.
  • Driver Alerts: Indicates when the vehicle is in an inducement state due to SCR system issues.

NOx Warning And Inducement System

NOx Warning And Inducement System provides detailed information on warning and inducement levels in NOx control systems.

• Warning/Inducement Levels:

  • Level 1 (Low Severity).
  • Level 2 (Medium Severity).
  • Level 3 (Severe).

• Status for Each Level: Inactive, Enabled but not active, Active, Not Supported.

• Historical Data: Engine hours with incorrect reagent, consumption rate, dosing interruptions, EGR DTCs, NOx control DTCs.

• Diagnostic Significance: Provides a more detailed breakdown of NOx warning and inducement levels and historical data related to NOx control system issues.

Engine Run Time for AECD

Engine Run Time for AECD (Auxiliary Emissions Control Device) reports the total time (in seconds) that each AECD has been active. AECDs are permitted emissions control strategies that may temporarily reduce emissions control effectiveness under specific conditions (e.g., engine protection, emergency situations).

• AECD Timers (TIME1, TIME2): May report total run time for AECD activation or separate timers for different levels of emissions control inhibition (e.g., up to 75% and beyond 75%).

• Diagnostic Significance:

  • AECD Usage Tracking: Provides data on how often AECDs are active, which can be relevant for emissions compliance and understanding vehicle operation under certain conditions.
  • Emissions Control System Behavior: Helps understand the vehicle’s emissions control strategy and when emissions control may be reduced due to AECD activation.