P0071

P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE





For a complete wiring diagram refer to Diagrams/Electrical.

Theory of Operation

Ambient Air Temperature Sensor performance looks at the outputs of three temperature sensors and compares them under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and intake air temperature sensors will be compared. If the engine coolant and intake air temperature sensors agree and the ambient air temperature does not agree, the ambient air temperature sensor is declared as irrational.

- When Monitored:

Engine off time is greater than 480 minutes. Ambient temperature is greater than 4° C (38° F).

- Set Condition:

After a calibrated amount of cool down time the BCM compares the ECT Sensor, IAT Sensor, and the Ambient Air Temp Sensor values. If the IAT Sensor value is not within 10° C (50° F) of the other two temperature sensors. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. ACTIVE DTC

NOTE: Diagnose any CAN - C Communication DTCs before continuing.

Start the engine.

Allow the engine to reach normal operating temperature.

With a scan tool, select View DTCs.

NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.

Is the DTC Active or Pending at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition

2. AAT SENSOR VOLTAGE ABOVE 4.6 VOLTS

Turn the ignition off.

Disconnect the AAT sensor harness connector.

Ignition on, engine not running.

With a scan tool, read the AAT voltage.

Is the voltage above 4.6 volts?

Yes

- Go To 3

No

- Go To 4

3. AAT SENSOR





Connect a jumper wire between the (G31) AAT Signal circuit and the (G931) Sensor ground circuit in the AAT Sensor harness connector.

With a scan tool, read the AAT voltage.

Is the voltage below 1.0 volt with the jumper wire installed?

Yes

- Replace the AAT Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 4

NOTE: Remove the jumper wire before continuing.

4. (G31) AAT SIGNAL CIRCUIT HIGH RESISTANCE

Turn the ignition off.

Reconnect the AAT sensor harness connector.

Using a voltmeter perform a voltage drop test. Backprobe the (G31) AAT Signal circuit at the AAT Sensor harness connector and the FCM.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Start the engine and allow it to reach normal operating temperature.

Monitor the voltmeter.

Is the voltage below 0.5 volts?

Yes

- Go To 5

No

- Repair the high resistance in the (G31) AAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

5. (G931) SENSOR GROUND CIRCUIT HIGH RESISTANCE

Turn the ignition off.

Using a voltmeter perform a voltage drop test. Backprobe the (G931) Sensor ground circuit at the AAT Sensor harness connector and the FCM.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Start the engine and allow it to reach normal operating temperature.

Monitor the voltmeter.

Is the voltage below 0.5 volts?

Yes

- Go To 6

No

- Repair the high resistance in the (G931) Sensor ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. FRONT CONTROL MODULE

NOTE: Before continuing, check the FCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform BODY VERIFICATION TEST. Body Verification Test

No

- Replace the Front Control Module.
- perform BODY VERIFICATION TEST. Body Verification Test