P0071 Ambient Air Temperature sensor performance

P0071 Ambient Air Temperature sensor performance - Engine off time greater that 480 minutes, ambient temperature greater than -7°C (19.4°F). Set conditions, after a calibrated amount of cool down time, the PCM compares the AAT, ECT, and IAT sensor values. If the AAT sensor value is not within 10°C (18°F) of the other temperature sensors, the AAT sensor is declared as irrational. Default actions, the MIL light will illuminate, if the vehicle is equipped with the stop/start feature, the system will be disabled when this DTC is active.

Possible causes:

• High resistance in the AAT signal circuit.
• High resistance in the AAT sensor ground circuit.
• Ambient Air Temperature (AAT) sensor.
• Totally Integrated Power Module (TIPM) or Body Control Module (BCM).

Diagnose code P0071-Ambient Air Temperature sensor performance

Step 1. Check for an active condition

Turn the ignition off, allow the vehicle to sit with the ignition off in an environment where the temperature is consistent and above -7°C (19.4°F) until the engine coolant temperature is equal, or loose to the environmental ambient temperature. Turn the ignition on, with the scan tool, compare the AAT, ECT, and IAT sensor values

Is the AAT sensor value within 10°C (18°F) of the other two sensor values ?

Yes, perform the PCM intermittent condition.

No, go to step 2.

Step 2. Check for high resistance in the AAT signal circuit

Turn the ignition off, disconnect the AAT sensor harness connector. Disconnect the TIPM/BCM harness connector, measure the resistance of the AAT signal circuit between the AAT sensor harness connector and the TIPM/BCM harness connector.

Is the resistance below 3.0 Ohms ?

Yes, go to step3.

No, repair the AAT signal circuit for an open or high resistance.

Step 3. Check for high resistance in the AAT sensor ground circuit

Measure the resistance of the AAT sensor ground circuit between the AAT sensor harness connector and the TIPM/BCM harness connector.

Is the resistance below 3.0 Ohms ?

Yes, go to step 4.

No, repair the AAT sensor ground for an open or high resistance.

Step 4. Ambient Air Temperature sensor

Turn the ignition off, reconnect the TIPM/BCM harness connector. Turn rhe ignition on, with the scan tool, read DTC. The P0073-AAT sensor circuit high, should display as active or pending with the AAT harness connector disconnected. Conenct a jumper between the AAT signal circuit and the AAT sensor ground circuit at the AAT sensor harness connector. The P0072-AAT sensor circuit low, should display as active or pending with the jumper in place.

Do the DTC display as described above ?

Yes, replace the Ambient Temperature sensor.

No, go to step 5.

Step 5. Check related PCM and component connections

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