Seeing the ‘check engine light’ illuminate on your dashboard without understanding why can be unsettling. That’s why having a solution to help decipher Diagnostic Trouble Codes (DTCs) is essential, allowing you to pinpoint your vehicle’s issue and take appropriate action, especially for Chevrolet vehicles.
What is an OBD2 Code?
A DTC, or Diagnostic Trouble Code, is a fault code used to identify malfunctions in a vehicle. While the malfunction indicator lamp (MIL), commonly known as the check engine light, simply alerts drivers to a problem, a DTC specifies the nature of the problem and its location within the vehicle’s systems. DTCs are also referred to as vehicle engine fault codes and can be accessed using a scanner that connects to a vehicle’s OBD2 port.
A basic understanding of DTCs can be invaluable for Chevrolet owners and fleet managers dealing with Chevrolets. Continue reading to learn more about OBD2 codes, how they function, and how you can interpret them for your Chevrolet vehicle.
The Origin of OBD2 Codes
DTCs are generated by a vehicle’s onboard diagnostic system (OBD) whenever a fault is detected. The OBD system diagnoses the fault and signals the DTC through visible warnings, such as turning on the check engine light. It also enables external devices, like an OBD2 scanner, to interact with the vehicle’s onboard computer system in Chevrolet and other vehicles.
Over the years, various versions of OBD interfaces were used; these interfaces, now known as OBDI, varied significantly between manufacturers. Today, two primary standards are used to read DTCs:
- OBD2: Ideal for light- and medium-duty vehicles, including most Chevrolet cars and trucks.
- J1939: Best suited for heavy-duty vehicles and equipment.
With the implementation of OBDII, the Society of Automotive Engineers (SAE) developed a standardized list of DTCs containing fault codes common across all manufacturers. This standardization is particularly helpful for understanding common Chevrolet OBD2 codes.
While OBDII is widely adopted, it’s important to note that manufacturer-specific DTCs still exist. Manufacturers like Chevrolet may create their own DTCs to supplement the universal code list if needed for specific vehicle features. However, these manufacturer-specific codes can be harder to interpret without specialized tools or a mechanic familiar with Chevrolet systems.
Does Your Chevrolet Use OBD2 or J1939?
OBD2 Compatibility:
- Cars and light trucks manufactured and sold in North America after January 1, 1996, are mandated to be equipped with OBD-II. This includes virtually all modern Chevrolet passenger vehicles.
J1939 Compatibility:
- Most vehicles or equipment with diesel engines are J1939 compatible.
- It is the industry standard for most heavy-duty trucks and buses. This is less common for typical Chevrolet consumer vehicles but might apply to some heavy-duty Chevrolet trucks or commercial vehicles.
If you’re unsure whether your Chevrolet vehicle is OBD2 or J1939 compliant, consult your vehicle’s manual, check online resources specific to your Chevrolet model, or contact your Chevrolet dealership to confirm compatibility. For most Chevrolet owners, OBD2 is the relevant standard.
Decoding Chevrolet OBD2 Codes: Reading the Code Structure
OBD2 DTCs are composed of five characters. Each character provides specific information about the vehicle’s problem, crucial for diagnosing issues in your Chevrolet.
The first character is always a letter, indicating the affected control system:
- P (Powertrain): Relates to the engine, transmission, fuel system, and associated accessories. This is very common for Chevrolet OBD2 codes.
- C (Chassis): Refers to mechanical systems outside the passenger compartment, such as steering, suspension, and braking systems in your Chevrolet.
- B (Body): Indicates issues with parts primarily located in the passenger compartment area of the Chevrolet, like airbags, power windows, or seats.
- U (Network): Pertains to the vehicle’s onboard computer and communication systems, relevant in modern Chevrolets with complex electronics.
The second character is a digit, typically 0 or 1, showing the code’s standardization:
- 0: Indicates a generic, standardized SAE (Society of Automotive Engineers) code. All vehicles adhering to the OBDII standard, including Chevrolets, adopt generic codes for common issues.
- 1: Signifies a manufacturer-specific code. These codes are unique to a specific vehicle brand or model, such as Chevrolet, and are generally less common in initial diagnoses.
- 2 or 3: Rarer and their meanings depend on the preceding letter. Mostly, 2 or 3 indicate a manufacturer-specific code, with few exceptions.
The third character is also a digit, ranging from 1 to 8. This reveals the specific subsystem at fault in your Chevrolet:
- 1: Fuel or air metering system issues.
- 2: Fuel or air metering injection system problems.
- 3: Ignition system malfunctions.
- 4: Emission control system faults – very relevant for many Chevrolet OBD2 codes.
- 5: Vehicle speed controls and idle control system issues.
- 6: Computer output circuit problems.
- 7 & 8: Transmission-related problems.
The fourth and fifth characters are read together as a two-digit number from 0 to 99, known as the specific fault index. These digits pinpoint the exact nature of the vehicle’s problem, providing a precise description within the subsystem identified, crucial for accurate Chevrolet repairs.
If you’re uncertain about the meaning of a specific Chevrolet OBD2 code, always consult your Chevrolet vehicle manufacturer documentation or a repair manual for detailed explanations.
Interpreting Chevrolet OBD2 Codes: A Practical Example
Each DTC corresponds to a specific vehicle malfunction, such as an engine misfire in cylinder one. Let’s decode a common Chevrolet OBD2 code example: P0128.
- P: Indicates the problem is in the Powertrain system, common for engine-related Chevrolet OBD2 codes.
- 0: Shows this is a generic code, not Chevrolet manufacturer-specific, following SAE standards.
- 1: Reveals the issue is within the fuel and air metering subsystem.
- 28: The specific fault index.
Based on this breakdown, the Chevrolet OBD2 code P0128 points to an issue with the engine coolant temperature being below the thermostat regulating temperature. This is valuable information for a Chevrolet owner or mechanic to start diagnosing the cooling system.
Common Chevrolet OBD2 Codes and Their Meanings
Certain Chevrolet OBD2 codes are more frequently encountered than others. Here’s a list of common codes you might find in your Chevrolet and their corresponding malfunctions:
- P0442: Small Evaporative Emission System Leak Detected. This is a common emission-related Chevrolet OBD2 code, often indicating a leak in the fuel vapor recovery system.
- P0606: PCM (Powertrain Control Module) Malfunction – a fault within the vehicle’s computer system.
- P0101: Mass Air Flow (MAF) Sensor Circuit Range/Performance Problem. Issues with the sensor measuring air intake are common Chevrolet OBD2 concerns.
- P0110: Intake Air Temperature Sensor Circuit Malfunction. Another air intake related sensor issue.
- P0500: Vehicle Speed Sensor Malfunction. Problems with the sensor that measures vehicle speed.
- P0706: Transmission Range Sensor Circuit Range/Performance. Relates to issues with the transmission range sensor.
It’s crucial to remember that while Chevrolet OBD2 codes are helpful in identifying a vehicle malfunction, they don’t explain why the problem occurred. Further diagnosis by a qualified mechanic is necessary to pinpoint and address the root cause of the issue in your Chevrolet.
Reading J1939 DTCs in Heavy-Duty Chevrolet Applications
While less common in typical Chevrolet consumer vehicles, some heavy-duty Chevrolet trucks or commercial vehicles might use the J1939 standard. A J1939 DTC contains four fields that transmit fault information:
- Suspect Parameter Number (SPN): Represents the specific parameter with the error. Each defined SPN can be used in a DTC.
- Failure Mode Identifier (FMI): Indicates the nature and type of error, such as value range violations (high or low), sensor short circuits, incorrect update rates, or calibration errors.
- Occurrence Counter (OC): Counts the number of times the error condition has occurred for each SPN, storing this count even when the error is no longer active.
- SPN Conversion Method (CM): Defines the byte alignment within the DTC. A value of “0” represents a standard method. A value of “1” indicates distinctions between previously valid methods.
DTC Scanning Tools for Chevrolet Fleet Managers
Scanners that read OBD2 codes, known as OBD2 scanners, are widely available for purchase. However, for fleet managers responsible for multiple Chevrolet vehicles, manually checking each vehicle every time the check engine light comes on can be inefficient.
That’s why selecting a fleet management solution that includes maintenance tools, like Samsara, is important. These tools simplify DTC identification, especially for a fleet of Chevrolet vehicles. Samsara’s vehicle gateways plug directly into the vehicle’s OBD2 port and transmit OBD2 data, including DTCs, to the cloud. This means if a Chevrolet OBD2 code appears, it automatically shows up on your Samsara dashboard, or you can opt to receive an alert.
If multiple vehicles in your Chevrolet fleet experience DTC issues, a telematics solution with a DTC tool helps you quickly identify the problem, enabling you to schedule necessary maintenance efficiently and minimize downtime for your Chevrolet vehicles.
Easily Understand Chevrolet OBD2 Codes with Telematics
Seeing a check engine light without knowing why can be stressful for any driver, especially those managing a Chevrolet. That’s why having a telematics solution like Samsara to help understand Chevrolet OBD2 codes is invaluable. It allows for quick identification of vehicle problems and prompt action.
Samsara’s vehicle gateway connects directly to a Chevrolet vehicle’s OBD2 port (or J1939 for applicable vehicles), transmitting DTC information directly to the Samsara dashboard. Alerts can be activated for DTC occurrences using the “Vehicle Fault” alert feature. You can also use Samsara’s DTC filtering feature to prioritize alerts for the most critical Chevrolet OBD2 codes for your fleet.
To learn more about how Samsara can help you read and address Chevrolet OBD2 codes and streamline your fleet maintenance, sign up for a free trial or explore Samsara’s fleet maintenance solutions.
