OBD Code P0113: Intake Air Temperature Sensor 1 Circuit High Input Explained

The trouble code P0113 is a common diagnostic trouble code (DTC) within the OBD-II system, indicating an issue with the Intake Air Temperature (IAT) Sensor circuit. Specifically, Obd Code P0113 signals “Intake Air Temperature Sensor 1 Circuit High Input.” This article will delve into the specifics of this code, exploring its meaning, potential symptoms, causes, and effective solutions, ensuring you have a comprehensive understanding to address this issue.

Understanding the P0113 Code: IAT Sensor and High Input

The Engine Control Unit (ECU), also known as the Powertrain Control Module (PCM) in many vehicles, relies on various sensors to optimize engine performance and efficiency. The Intake Air Temperature (IAT) sensor is crucial for measuring the temperature of the air entering your engine. This temperature reading is vital for the PCM to calculate the correct air-fuel mixture and ignition timing.

The IAT sensor is typically a thermistor, a type of resistor whose resistance changes with temperature. As the intake air temperature rises, the resistance of the thermistor decreases, and vice versa. The PCM supplies a 5-volt reference voltage to the IAT sensor. Changes in the sensor’s resistance affect the voltage signal returned to the PCM.

Code P0113 is triggered when the PCM detects an abnormally high voltage signal from the IAT sensor circuit. This “high input” indicates that the voltage is exceeding the expected range, typically above 5 volts. This situation usually implies a problem within the sensor circuit that is causing the PCM to interpret the intake air temperature as being extremely cold, even when it’s not.

Symptoms Associated with OBD Code P0113

Often, the most noticeable symptom of a P0113 code is the illumination of the Malfunction Indicator Lamp (MIL), commonly known as the Check Engine Light on your dashboard. However, in many cases, obd code p0113 might not present any other immediately apparent symptoms.

While less frequent, you might experience subtle symptoms like:

Slight decrease in fuel efficiency: An incorrect IAT reading can lead the PCM to miscalculate the air-fuel mixture, potentially making it richer than necessary, thus reducing fuel economy.
Minor hesitation or sluggishness: In some scenarios, the engine might exhibit slight hesitation or a lack of responsiveness, especially during cold starts, as the PCM might be using inaccurate temperature data.
Difficulty starting in cold weather: Although less common, an extremely high input signal could theoretically lead to starting issues in very cold conditions, as the system might incorrectly assume excessively low temperatures.

It’s important to note that these symptoms are generally mild and may not always be present, which underscores the importance of addressing the Check Engine Light even if the vehicle seems to be running normally.

Common Causes of P0113 Error Code

Several factors can lead to a P0113 code. Pinpointing the exact cause is crucial for effective repair. Here are the most common culprits:

Faulty IAT Sensor: The sensor itself might have failed internally. Thermistors can degrade over time or become damaged due to environmental factors.
Wiring or Connector Issues: This is a frequent cause.
- Loose or Corroded Connector: The electrical connector at the IAT sensor might be loose, corroded, or damaged, leading to poor electrical contact and incorrect signal transmission.
- Open Circuit: A break in the wiring of the IAT sensor’s ground or signal circuit can cause a high voltage reading. This could be due to physical damage, rodent activity, or wear and tear.
- Short to Voltage: The IAT sensor signal or reference circuit wiring might be shorting to a voltage source. This could occur if the wiring insulation is damaged and comes into contact with another wire carrying voltage.
Wiring Proximity to High Voltage Components: If the IAT sensor harness and wiring are routed too close to high-voltage components like the alternator or spark plug cables, electromagnetic interference can induce voltage into the IAT signal circuit, causing a false high input reading.
PCM Failure (Rare): While less likely, a fault within the PCM itself could cause it to misinterpret the IAT sensor signal or incorrectly set the P0113 code. This is usually diagnosed after ruling out all other potential causes.

An Intake Air Temperature (IAT) Sensor, the component often responsible for triggering the P0113 code.

Diagnosing and Fixing OBD-II Code P0113

Diagnosing and resolving a P0113 code usually involves a systematic approach. Here’s a step-by-step guide to help you troubleshoot and fix this issue:

Initial Scan and Reading: Use an OBD-II scan tool to confirm the presence of the P0113 code and check for any other related codes. Crucially, check the IAT sensor reading on the scan tool.
- Logical Reading: If the IAT reading appears plausible (e.g., close to ambient temperature), the problem might be intermittent. Carefully inspect the wiring and connectors for any signs of looseness or corrosion.
- Illogical Reading (Very Low Temperature): If the IAT reading is extremely low (e.g., below -30 degrees Fahrenheit), proceed to the next steps.
Connector and Wiring Inspection:
- Visual Inspection: Carefully examine the IAT sensor connector and wiring harness for any visible damage, such as frayed wires, melted insulation, corrosion, or loose connections.
- Connector Check: Ensure the connector is securely attached to the IAT sensor. Clean the connector pins with an electrical contact cleaner if you notice corrosion.
Bypass Test (Jumper Wire Method):
- Disconnect IAT Sensor: Unplug the electrical connector from the IAT sensor.
- Jumper Wire Installation: Use a jumper wire to connect the signal and ground circuits within the harness connector (the connector that was plugged into the sensor, not the sensor itself). Refer to your vehicle’s wiring diagram to correctly identify the signal and ground pins.
- Scan Tool Reading: With the jumper wire in place, check the IAT reading on your scan tool.
  - High Reading (Maxed Out): If the reading now shows a very high temperature (e.g., 280°F or higher), this indicates that the wiring is likely intact, and the issue might be with the IAT sensor itself or the connection. Proceed to sensor replacement or further connection checks.
  - Still Low or No Reading: If the reading remains low or there is no reading at all, the problem is likely in the wiring or the PCM reference voltage supply.
Ground Circuit Test:
- Jumper to Chassis Ground: Remove the jumper wire from the signal and ground pins. Install a jumper wire between the IAT signal circuit pin in the harness connector and a known good chassis ground point on the vehicle.
- Scan Tool Reading: Check the IAT reading on the scan tool again.
  - High Reading (Maxed Out): If the reading is now maxed out, this suggests an open circuit in the IAT ground wire. Inspect the ground wire for breaks or damage and repair as needed.
  - Still Low or No Reading: If the reading remains low or absent, proceed to the next step, focusing on the signal circuit and reference voltage.
5-Volt Reference Voltage Check:
- DVOM Measurement: Use a Digital Volt-Ohm Meter (DVOM) to check for the 5-volt reference voltage at the IAT sensor harness connector (with the sensor disconnected and ignition ON). Probe between the 5-volt reference pin and the ground pin in the connector. Again, consult your vehicle’s wiring diagram for pin identification.
  - 5-Volt Present: If 5 volts is present, the reference voltage supply from the PCM is likely good. The issue might be an open in the signal wire or a faulty sensor.
  - No 5-Volt Reference: If there’s no 5-volt reference, there could be a problem with the PCM’s voltage regulator or an open circuit in the 5-volt reference wire. Further PCM and wiring diagnosis may be needed.
Signal Circuit Continuity Test:
- PCM Connector Disconnection: Turn the ignition OFF and disconnect the PCM connector. Always take precautions when working with PCM connectors, such as disconnecting the battery.
- Continuity Check: Use a DVOM in continuity mode to check for continuity in the IAT signal circuit between the PCM connector pin and the IAT sensor connector pin. Refer to wiring diagrams for pin locations on both connectors.
  - No Continuity: If there’s no continuity, there is an open circuit in the signal wire. Locate and repair the break.
  - Continuity Present: If continuity is good, and you’ve ruled out other wiring issues and confirmed 5-volt reference, the IAT sensor itself is the most likely culprit.
IAT Sensor Replacement: If all wiring and voltage tests pass, replace the IAT sensor with a new, quality replacement sensor. After replacement, clear the P0113 code using a scan tool and re-evaluate the system to ensure the code does not return.

Related OBD-II Trouble Codes

P0095 – Intake Air Temperature Sensor 2 Circuit
P0096 – Intake Air Temperature Sensor 2 Circuit Range/Performance
P0097 – Intake Air Temperature Sensor 2 Circuit Low Input
P0098 – Intake Air Temperature Sensor 2 Circuit High Input
P0099 – Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic
P0110 – Intake Air Temperature Circuit Malfunction
P0111 – Intake Air Temperature Circuit Range/Performance Problem
P0112 – Intake Air Temperature Sensor 1 Circuit Low Input
P0114 – Intake Air Temperature Sensor 1 Circuit Intermittent
P0127 – Intake Air Temperature Too High

Conclusion

Addressing obd code p0113 promptly is important to ensure optimal engine performance and fuel efficiency. While often not associated with severe drivability issues, a persistent Check Engine Light can mask other potentially more critical problems. By systematically diagnosing the possible causes, from sensor malfunction to wiring faults, and following the outlined troubleshooting steps, you can effectively resolve the P0113 code and restore your vehicle’s system to proper working order. Remember, if you’re uncomfortable performing these diagnostic steps, it’s always best to consult a qualified automotive technician.

Disclaimer: This information is for informational purposes only and should not be considered professional repair advice. We are not liable for any actions taken based on this information. Always consult a qualified technician for vehicle repairs.