P0071
P0071 - Ambient Air Temperature Sensor Performance
For wiring diagrams, refer to.
Theory of Operation
The PCM compares the ambient air temperature sensor, engine coolant temperature sensor, and intake air temperature sensor values. If one value is not within a specific range of the other two, a second comparison is made after a short drive cycle. If the ambient air temperature sensor value is still not within the range, it is determined to be irrational.
• When Monitored: With engine run time greater than 1 minute, ambient temperature more than -64 °C (-83 °F), following an engine off period of more than 480 minutes.
• Set Condition: The PCM compares the ambient air temperature sensor, engine coolant temperature sensor, and intake air temperature sensor values. If the engine coolant temperature sensor and intake air temperature sensor are within a specific range of each other, but the ambient air temperature sensor is not, the ambient air temperature sensor value is declared irrational. Two trip fault. Three good trips to turn off the MIL.
• Always perform the pre-diagnostic troubleshooting procedure before proceeding. Refer to => Non-DTC Based Diagnostics. Pre-Diagnostic Troubleshooting Procedure
Test Step 1 - DTC is Active
• Diagnose and repair any CAN C communication or message DTCs in any module before continuing with this procedure.
• Turn the ignition ON.
• With the scan tool, select view DTCs and review the DTC environmental data for this DTC.
Is the good trip counter greater than 0?
Yes
• Go to Test Step 2 => [ Test
Step 2 - Ambient Air Temperature ]
No
• Go to Test Step 3 => [ Test
Step 3 - AAT Signal Circuit Shorted to Voltage ]
Test Step 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 more than -7 °C (19.4 °F) until the actual engine temperature is equal to actual ambient temperature.
• Turn the ignition ON.
• With a scan tool, compare the engine temperature sensor values of the ambient temperature sensor, engine coolant temperature sensor, intake air temperature sensor, and, if equipped, the engine oil temperature sensor.
Is the ambient air temperature sensor value within 10 °C (18 °F) of the other sensor values?
Yes
• Refer to the checking for an intermittent DTC diagnostic procedure. Refer => Non-DTC Based Diagnostics.
No
• Go to Test Step 3 => [ Test
Step 3 - AAT Signal Circuit Shorted to Voltage ]
Test Step 3 - AAT Signal Circuit Shorted to Voltage
• Turn the ignition OFF.
• Disconnect the ambient air temperature sensor harness connector.
• Disconnect the C4 totally integrated power module harness connector.
• Turn the ignition ON.
• Measure the voltage of the AAT signal circuit in the ambient air temperature sensor harness connector.
Is there any voltage present?
Yes
• Repair the short to voltage in the AAT signal circuit.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
No
• Go to Test Step 4 => [ Test
Step 4 - AAT Signal Circuit Shorted to Ground ]
Test Step 4 - AAT Signal Circuit Shorted to Ground
• Turn the ignition OFF.
• Measure the resistance between ground and the AAT signal circuit in the ambient air temperature sensor harness connector.
Is the resistance more than 100 ohms?
Yes
• Go to Test Step 5 => [ Test
Step 5 - AAT Signal Circuit Shorted to AAT Return Circuit ]
No
• Repair the short to ground in the AAT signal circuit.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
Test Step 5 - AAT Signal Circuit Shorted to AAT Return Circuit
• Measure the resistance between the AAT signal circuit and the AAT return circuit in the ambient air temperature sensor harness connector.
Is the resistance more than 100 ohms?
Yes
• Go to Test Step 6 => [ Test
Step 6 - Excessive Resistance in AAT Signal Circuit ]
No
• Repair the short between the AAT signal circuit and the AAT return circuit.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
Test Step 6 - Excessive Resistance in AAT Signal Circuit
• When checking circuits at the totally integrated power module, be careful not to damage or distort the connector terminals. Improper measurement technique could result in poor pin to terminal contact.
• Measure the resistance of the AAT signal circuit between the ambient air temperature sensor harness connector and the C4 totally integrated power module harness connector.
Is the resistance less than 5.0 ohms?
Yes
• Go to Test Step 7 => [ Test
Step 7 - Excessive Resistance in AAT Return Circuit ]
No
• Repair the excessive resistance in the circuit.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
Test Step 7 - Excessive Resistance in AAT Return Circuit
• When checking circuits at the totally integrated power module, be careful not to damage or distort the connector terminals. Improper measurement technique could result in poor pin to terminal contact.
• Measure the resistance of the AAT return circuit between the ambient air temperature sensor harness connector and the C4 totally integrated power module harness connector.
Is the resistance less than 5.0 ohms?
Yes
• Go to Test Step 8 => [ Test
Step 8 - Ambient Air Temperature Sensor Signal Voltage ]
No
• Repair the excessive resistance in the circuit.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
Test Step 8 - Ambient Air Temperature Sensor Signal Voltage
• Turn the ignition OFF.
• Connect the C4 totally integrated power module harness connector.
• Turn the ignition ON.
• With the scan tool, read the ambient air temperature sensor signal voltage.
• The ambient air temperature sensor signal voltage should be approximately 5.0 volts (plus or minus 0.2 volts) with the ambient air temperature sensor connector disconnected.
• Turn the ignition OFF.
• Connect a jumper wire between the AAT return circuit and the AAT signal circuit in the ambient air temperature sensor harness connector.
• Turn the ignition ON.
• With the scan tool, read the ambient air temperature sensor signal voltage.
• The ambient air temperature sensor signal voltage should be approximately 0.0 volts (plus or minus 0.2 volts) with the jumper wire in place.
Is the voltage within the ranges specified?
Yes
• Go to Test Step 9 => [ Test
Step 9 - Ambient Air Temperature Sensor ]
No
• Go to Test Step 10 => [ Test
Step 10 - Totally Integrated Power Module ]
Test Step 9 - Ambient Air Temperature Sensor
• Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the ambient air temperature sensor and the totally integrated power module.
• Look for any chafed, pierced, pinched, or partially broken wires.
• Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.
• 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.
• Refer to any technical service bulletins that may apply.
Were any problems found?
Yes
• Repair as necessary.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
No
• Replace the ambient air temperature sensor.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
Test Step 10 - Totally Integrated Power Module
• Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the ambient air temperature sensor and the totally integrated power module.
• Look for any chafed, pierced, pinched, or partially broken wires.
• Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.
• 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.
• Refer to any technical service bulletins that may apply.
Were any problems found?
Yes
• Repair as necessary.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior
No
• Replace the totally integrated power module.
• Perform the Body Verification Test. Refer to => Non-DTC Based Diagnostics. Body Interior