Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Sensor, Ambient Temperature: Operation
The Body Control Module (BCM) is the master of the ambient air temperature. It provides raw ambient temperature and averaged ambient temperature. Raw ambient temperature is what the sensor reads. This information is provided to the Powertrain Control Module (PCM) at a very fast rate. Averaged ambient temperature is a complex algorithm and it is the temperature that is provided to the customer (displayed on the Instrument Panel Cluster/IPC and radio module) at a rate of once per second or upon a temperature change. All other modules, for example heated seats, use this averaged ambient temperature.
Auto ON Feature and Ambient Temperature
The vehicle needs to be OFF for about 3.5 hours before it will take in raw or instantaneous readings and provide it to the customer. This is to ensure that false readings are not displayed due to engine heat soak. Readings also depend on where the vehicle is stored. If the vehicle is parked in a garage for 5 hours where it could be 10°C (50°F) and outside temperature is -1°C (30°F), then the vehicle would display 10°C (50°F). The customer would have to drive the vehicle for 20 seconds above 32 km/h (20 mph) before it would start to update (± 1° is allowed per second) and trend towards true outdoor temperature of -1°C (30°F). If the outside ambient temperature is cold enough to warrant the auto comfort features such as heated seats and heated steering wheel but the vehicle is stored in a garage where the temperature is at an amount that does not warrant these features, they will not auto activate.
To get the most accurate ambient temperature readings, the vehicle should be driven.
For diagnostic information about the ambient air temperature sensor, Refer to SENSOR, AMBIENT TEMPERATURE, DIAGNOSIS AND TESTING .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.