P0071

P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE





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 (18° 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.

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 DTC Active or Pending at this time?

Yes

- Go To 3

No

- Go To 2


2. AMBIENT AIR TEMPERATURE

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 to ambient temperature.

Turn the ignition on.

With a scan tool, compare the AAT, ECT, and IAT sensor values.

Is the Ambient Air Temperature Sensor value within 10° C (18° F) of the other two sensor values?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 3


3. AAT SENSOR VOLTAGE

Turn the ignition off.

Disconnect the AAT sensor harness connector.

Ignition on, engine not running.

With a scan tool, read the AAT voltage.


NOTE: The sensor voltage should be approximately 5.0 volts (plus or minus 0.1 volt) with the connector disconnected.

Does the scan tool display the voltage as described above?

Yes

- Go To 4

No

- Go To 5


4. AAT SENSOR





Turn the ignition off.

Connect a jumper wire between the (G31) AAT Signal circuit and the (G931) Sensor Ground circuit in the Ambient Air Temperature Sensor harness connector.

Turn the ignition on.

With a scan tool, read the Ambient Air Temperature Sensor voltage.


NOTE: The sensor voltage should be approximately 0.0 volts (plus or minus .1 volt) with the jumper wire in place.

Does the scan tool display the voltage as described above?

Yes

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

No

- Go To 5

NOTE: Remove the jumper wire before continuing.


5. (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 C4 TIPM harness connector.

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


6. (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 C4 TIPM harness connector.


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 7

No

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


7. TOTALLY INTEGRATED POWER MODULE

NOTE: Before continuing, check the TIPM 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 VER - 1. Body Verification Test

No

- Replace the Totally Integrated Power Module.
- Perform BODY VERIFICATION TEST VER - 1. Body Verification Test