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

Navigating the complexities of your vehicle’s onboard diagnostics system can be daunting, especially when faced with a check engine light. Among the numerous trouble codes you might encounter, Car Scan Code P0113 is a common one related to your vehicle’s Intake Air Temperature (IAT) sensor. As an expert from carcodepro.com, I’m here to break down what this code means, its potential causes, symptoms, and how to troubleshoot it effectively.

Understanding the P0113 Code: IAT Sensor Circuit High Input

The P0113 diagnostic trouble code is a generic powertrain code that applies across vehicles equipped with OBD-II systems. Essentially, it indicates that the Engine Control Unit (ECU), also known as the Powertrain Control Module (PCM), has detected an abnormally high voltage signal from the Intake Air Temperature (IAT) sensor circuit.

To understand this further, let’s delve into the function of the IAT sensor. This sensor is crucial for your engine’s performance and efficiency. It measures the temperature of the air entering the engine’s intake manifold. This temperature reading is vital for the PCM to calculate the correct air-fuel mixture. The PCM provides a 5-volt reference voltage to the IAT sensor.

The IAT sensor itself is 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. This change in resistance affects the voltage signal sent back to the PCM. Low air temperature results in a high signal voltage, and high air temperature results in a low signal voltage.

Code P0113 is triggered when the PCM registers a signal voltage from the IAT sensor circuit that is excessively high, specifically higher than the expected range, often above 5 volts. This “high input” condition signals a potential issue within the IAT sensor circuit.

Decoding the Symptoms of a P0113 Code

One of the frustrating aspects of the car scan code P0113 is that it often presents with minimal to no noticeable symptoms beyond the illumination of the Malfunction Indicator Lamp (MIL), commonly known as the Check Engine Light. You might see “Check Engine,” “Service Engine Soon,” or a similar warning light on your dashboard.

However, in some cases, depending on the vehicle and the specific nature of the fault, you might experience subtle drivability issues. These are less common with a P0113 code alone but could potentially include:

• Slight decrease in fuel efficiency: If the PCM is receiving incorrect IAT readings, it could potentially miscalculate the air-fuel mixture, leading to less optimal fuel consumption.
• Minor hesitation or rough idle: In rare scenarios, an extreme IAT reading error could contribute to minor engine performance issues, although this is less typical for a P0113.

It’s important to note that the absence of obvious symptoms doesn’t diminish the importance of addressing a P0113 code. Running your vehicle with unresolved sensor issues can potentially lead to longer-term problems or mask other underlying conditions.

Potential Causes Behind a P0113 Code

Several factors can lead to a car scan code P0113. Pinpointing the exact cause is crucial for effective repair. Here are the 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 at the IAT Sensor: This is a frequent cause. Problems can include:
  • Loose or corroded connector: The electrical connector at the IAT sensor could be loose, damaged, or corroded, leading to poor electrical contact.
  • Damaged wiring: The wires leading to or from the IAT sensor can be damaged – frayed, broken, or shorted.
  • Open circuit in IAT ground or signal circuit: A break in the ground or signal wire can disrupt the circuit and cause a high voltage reading.
  • Short to voltage in IAT signal or reference circuit: The signal or reference wire might be shorting to a voltage source, causing an artificially high voltage reading.
• Wiring proximity to high-voltage components: If the IAT sensor harness or wiring is routed too close to high-voltage components like the alternator or spark plug cables, electromagnetic interference can induce voltage into the IAT signal circuit, triggering the P0113 code.
• PCM Failure (Less Likely): While less common, a fault within the PCM itself could, in rare cases, cause a misinterpretation of the IAT sensor signal or an issue with the reference voltage supply. This is usually considered a last resort diagnosis after ruling out other possibilities.

Diagnosing and Resolving Car Scan Code P0113

Troubleshooting a P0113 car scan code requires a systematic approach. Here’s a step-by-step guide to help you diagnose and potentially resolve the issue:

1. Initial Scan Tool Check:

   • 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. Is there a reading at all? Is it plausible?
     • Logical Reading: If the IAT reading seems reasonable (e.g., close to ambient temperature), the problem might be intermittent or related to a temporary wiring glitch.
     • Illogical Reading (e.g., extremely low like -30 degrees or lower): This strongly suggests a circuit issue or sensor malfunction.

2. Connector and Wiring Inspection:

   • Visually inspect the IAT sensor connector and wiring harness. Look for:
     • Signs of damage, corrosion, or loose connections at the connector.
     • Frayed, cracked, or broken wires.
     • Wiring routed too close to high-voltage components.
   • Securely reseat the IAT sensor connector to ensure a good electrical connection. Sometimes, simply unplugging and replugging the connector can resolve intermittent connection issues.

3. Jumper Wire Test (Circuit Integrity):

   • If the IAT reading is implausibly low (e.g., -30 degrees or lower): This test helps determine if the wiring is intact.
   • Unplug the IAT sensor connector.
   • Use a jumper wire to connect the signal and ground circuits within the harness connector. (Refer to your vehicle’s wiring diagram for correct pin identification – crucial to avoid damage).
   • Observe the IAT reading on the scan tool.
     • Reading Maxed Out High (e.g., 280°F or higher): This indicates the wiring is likely good, and the problem might be the IAT sensor itself or the connector.
     • Reading Remains Low or No Reading: This suggests a problem in the wiring between the connector and the PCM, or potentially an issue with the PCM’s reference voltage supply.

4. Ground Circuit Test:

   • If the jumper wire test did not max out the reading:
   • Keep the jumper wire connected to the signal circuit in the harness connector.
   • Connect the other end of the jumper wire to a known good chassis ground.
   • Check the IAT reading on the scan tool again.
     • Reading Maxed Out High Now: This points to an open circuit specifically in the IAT ground circuit. You’ll need to trace and repair the ground wire.

5. 5-Volt Reference Voltage Check:

   • If you get no IAT reading at all on the scan tool, or the jumper wire tests are inconclusive:
   • Use a Digital Volt-Ohm Meter (DVOM) to check for the 5-volt reference voltage at the IAT sensor connector.
     • With the ignition ON and the IAT sensor disconnected, carefully probe the reference voltage pin in the harness connector with the positive lead of your DVOM and a known good ground with the negative lead.
     • You should measure approximately 5 volts.
     • No 5-volt reference: Indicates a potential issue with the PCM’s voltage supply or a break in the reference voltage wire.

6. Signal Circuit Continuity Check:

   • If the 5-volt reference is present:
   • Unplug the PCM connector (refer to your vehicle’s service manual for location and procedure – always disconnect the battery before unplugging PCM connectors).
   • Use your DVOM to check for continuity (resistance) on the IAT signal circuit between the PCM connector pin and the IAT sensor connector pin. (Again, wiring diagrams are essential for pin identification).
     • No Continuity (Open Circuit): Indicates a break in the signal wire that needs to be located and repaired.

7. IAT Sensor Replacement:

   • If wiring and reference voltage checks are normal, and the jumper wire test points to a sensor issue, the most likely culprit is a faulty IAT sensor.
   • Replace the IAT sensor with a new, quality replacement.

8. PCM as Last Resort:

   • PCM failure is rare. Only consider PCM diagnosis and replacement after thoroughly ruling out all other wiring, connector, and sensor issues. PCM diagnosis often requires specialized tools and expertise.

After performing any repairs, clear the P0113 code using your scan tool and monitor if it returns. Road test the vehicle to ensure the check engine light stays off and that there are no drivability issues.

Important Note: Always consult your vehicle’s specific repair manual or wiring diagrams for accurate procedures, connector pinouts, and safety precautions. If you are not comfortable with electrical diagnostics, it’s best to seek assistance from a qualified automotive technician.

For further assistance and community support, don’t hesitate to post your questions in our FREE car repair forums at carcodepro.com. Our community of experts and enthusiasts is ready to help you navigate your car repair journey.

Disclaimer: This information is for informational purposes only and not intended as professional repair advice. Always consult qualified professionals for vehicle repairs. We are not responsible for any actions taken based on this information.