Cause
Sensor heat soak from poor mounting or airflow
A temperature sensor reading the heat of the thing it is bolted to rather than the medium it is supposed to measure. It is a mounting and airflow fault, not a sensor fault, and the sensor is usually in perfect condition.
Intake air temperature is where it matters most. A sensor sited close to a hot manifold, or in a duct with little flow, reads accurately while the vehicle is moving and then climbs as soon as it stops — so the module believes the incoming air is far hotter than it is and pulls timing or enriches unnecessarily. The signature is a reading that rises when the vehicle stops and falls when it moves, which is the opposite of how ambient air behaves.
The causes are usually physical and recent. A sensor not seated to its depth, a missing insulating grommet, a heat shield left off after work, a duct rerouted, or an aftermarket intake that moved the sensor into the engine bay. Compare the reading against ambient after an overnight soak — they should agree closely, and a sensor that reads high on a cold engine has a mounting problem rather than a calibration one.
Typically a moderate job.
Codes this can cause (4)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0071 Ambient Air Temperature Sensor Circuit A Range/Performance Likely for this code Low
- P0127 Intake Air Temperature Too High Likely for this code Moderate
- P009A Intake Air Temperature/Ambient Air Temperature Correlation Moderate
- P0111 Intake Air Temperature Sensor 1 Circuit Range/Performance Bank 1 Moderate
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