P0071

P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE (PCM)

For a complete wiring diagram consult Diagrams/Electrical.

Theory of Operation


The PCM compares engine coolant temperature (ECT), intake air temperature (IAT), and ambient air temperature (AAT) under cold start conditions. Following a start to run delay time, the sensor values are compared. If the one sensor value is not within a specified range of the other two sensors, the value is determined to be irrational.

- When Monitored:
With engine off time greater than 480 minutes and ambient temperature greater than - 7° C (19.4° F).

- Set Condition:
After a calibrated amount of cool down time, the PCM compares the AAT, ECT, and IAT Sensor values. If one sensor value is not within 10° C (18° F) of the other temperature sensors for two consecutive trips, a DTC will set. Three good trips to turn off the MIL.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.


Diagnostic Test


1. DTC IS ACTIVE
Turn the ignition off.
If possible, allow the vehicle to sit with the ignition off for more than 480 minutes in an environment where the temperature is consistent and above - 7° C (19.4° F).
Test drive the vehicle. The vehicle must exceed 48 km/h (30 mph) during the test drive. Do not cycle the ignition off when the test drive is completed.
With a scan tool, select View DTCs.
Is the status Active or Pending for this DTC?

Yes


- Go to 3


No


- Go to 2




2. DTC SET IN TIPM
Turn the ignition on.
With a scan tool, read TIPM DTC.
Is the Ambient Air Temperature Sensor DTC(s) set?

Yes


- Perform the appropriate AAT (TIPM) DTC Test.


No


- Go to 3




3. COMMUNICATION DTC(S)
With a scan tool, check for any Communication DTC(S)
Are any Communication DTC(S) set?

Yes


- Perform the appropriate Communication Test.


No


- Go to 4




4. POWERTRAIN CONTROL MODULE (FCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
Look for the data to change or for the DTC to reset during the wiggle test.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes


- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test


No


- Replace the Powertrain Control Module (FCM).
- Perform the PCM Verification Test.Powertrain Verification Test