Intake Air Temperature Sensor Circuit Intermittent High Voltage (GM)
What does P1111 mean?
The P1111 code means the vehicle's onboard diagnostic system has detected: Intake Air Temperature Sensor Circuit Intermittent High Voltage (GM). This is a low severity code.
Common Symptoms
- Check Engine Light on
- Slightly rough cold start
- Minor decrease in fuel economy
- Engine may run slightly rich
- Occasional idle fluctuation
Probable Causes (Ranked by Likelihood)
- Faulty intake air temperature (IAT) sensor Very High
- Corroded or loose IAT sensor connector High
- Open or shorted IAT sensor wiring Moderate
- Poor ground connection for sensor circuit Moderate
- PCM issue Low
Step-by-Step Diagnostic Procedure
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Read IAT sensor data with a scan tool and compare to ambient temperature
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Inspect the IAT sensor connector for corrosion or looseness
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Test IAT sensor resistance with a multimeter (should change with temperature)
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Check the wiring harness between the IAT sensor and PCM for damage
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Wiggle test the connector while monitoring live data for signal dropout
Frequently Asked Questions
Is P1111 a serious code?
P1111 is generally a low-severity code. The engine will use a default value for intake air temperature, which may slightly affect fuel economy and emissions but will not cause major drivability problems.
Where is the IAT sensor located?
On most GM vehicles, the IAT sensor is built into the mass airflow (MAF) sensor assembly in the air intake duct. On some older models, it is a separate sensor in the intake manifold or air cleaner housing.
Can I replace the IAT sensor myself?
Yes. The IAT sensor is one of the easiest sensors to replace. On GM vehicles where it is integrated into the MAF sensor, you may need to replace the entire MAF assembly, which is still a straightforward job.