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 (50° F) of the other two temperature sensors. Two Trip Fault. Three good trips to turn off the MIL.

Possible Causes

(G31) AAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

(G31) AAT SIGNAL CIRCUIT OPEN

(K300) SENSOR GROUND CIRCUIT OPEN

(G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND

(G31) AAT SIGNAL CIRCUIT SHORTED TO THE (K300) SENSOR GROUND CIRCUIT

AMBIENT AIR TEMPERATURE SENSOR

CAN C BUS CIRCUITS OPEN OR SHORTED

BCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1.ACTIVE DTC

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

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

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2.(G31) AAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

NOTE: Visually inspect both the component and the BCM connectors. Look for damaged, partially broken wires, and backed out or corroded terminals.

Is the voltage above 5.2 volts?

Yes

Repair the short to voltage in the (G31) AAT Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 3

3.AAT SENSOR VOLTAGE ABOVE 4.6 VOLTS

Is the voltage above 4.6 volts?

Yes

Go To 4

Go To 7

4.AAT SENSOR

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

Yes

Replace the AAT Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 5
NOTE: Remove the jumper wire before continuing.

5.(G31) AAT SIGNAL CIRCUIT OPEN

Is the resistance below 5.0 ohms?

Yes

Go To 6

Repair the open in the (G31) AAT Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

6.(K300) SENSOR GROUND CIRCUIT OPEN

Is the resistance below 5.0 ohms?

Yes

Go To 9

Repair the open in the (K300) Sensor ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

7.(G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND

Is the resistance below 100 ohms?

Yes

Repair the short to ground in the (G31) AAT Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 8

8.(G31) AAT SIGNAL CIRCUIT SHORTED TO THE (K300) SENSOR GROUND CIRCUIT

Is the resistance below 5.0 ohms?

Yes

Repair the short between the (K300) Sensor ground circuit and the (G31) AAT Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 9

9.BCM

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

Were there any problems found?

Yes

Repair as necessary.
Perform the BODY VERIFICATION TEST. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE)

Replace the Body Control Module per Service Information.
Perform the BODY VERIFICATION TEST. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE)