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P0111






P0111-INTAKE AIR TEMPERATURE SENSOR RATIONALITY





For a complete wiring diagram Refer to the Wiring Information.

Theory of Operation

Intake 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 ambient air temperature sensors agree and the intake air temperature does not agree, the intake air temperature sensor is declared as irrational. If declared irrational a second comparison will be done after a short drive cycle.

- When Monitored:
The engine off time is greater than 480 minutes. Ambient Temperature if greater than -64° C (-83° F).

- Set Condition:
Once the vehicle is soaked for a calibrated engine off time and then driven over calibrated speed and load conditions for some calibrated time, the PCM compares the ambient, engine coolant, and intake air temperature sensor values. If engine coolant and ambient air temperature sensors agree with each other but intake air temperature does not agree with them, the intake air temperature sensor is declared as irrational. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Turn the ignition off.
2. 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).
3. 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.
4. 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. INTAKE AIR TEMPERATURE
1. Turn the ignition off.
2. 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.
3. Turn the ignition on.
4. With a scan tool, compare the AAT, ECT, and IAT sensor values.

Is the Intake 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 Test.

No

- Go To 3

3. IAT SENSOR VOLTAGE
1. Turn the ignition off.
2. Disconnect the Intake Air Temperature Sensor harness connector.
3. Turn the ignition on.
4. With a scan tool, read the Intake Air Temperature Sensor voltage.

NOTE: The sensor voltage should be approximately 5.0 volts (plus or minus.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. IAT SENSOR




1. With a scan tool, read the IAT voltage.
2. Connect a jumper wire between the (K21) IAT Signal circuit and the (K900) Sensor ground circuit in the IAT Sensor harness connector.

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

- Verify that there is good pin to terminal contact in the Sensor and Powertrain Control Module connectors. Replace the IAT Sensor if no problems were found with the connectors.
- Perform the POWERTRAIN VERIFICATION TEST.Powertrain Verification Test

No

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

5. EXCESSIVE RESISTANCE IN THE (K21) IAT SIGNAL CIRCUIT
1. Turn the ignition off.
2. Disconnect the C2 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 and PCM Pinout Box Adapter 8815-1 to perform diagnosis.

3. Using a voltmeter perform a voltage drop test. Backprobe the (K21) IAT Signal circuit at the IAT Sensor harness connector and probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

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 may result in possible serious or fatal injury.

4. Start the engine and allow it to reach normal operating temperature.
5. Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

- Go To 6

No

- Repair the open in the (K21) IAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. EXCESSIVE RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT
1. Turn the ignition off.
2. Move the voltmeter leads to backprobe the (K900) Sensor Ground circuit at the IAT Sensor harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

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 may result in possible serious or fatal injury.

3. Start the engine and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 volts?

Yes

- Go To 7

No

- Repair the open in the (K900) Sensor ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

7. (K21) IAT SIGNAL CIRCUIT SHORTED TO VOLTAGE




1. Turn the ignition off.
2. Disconnect the special tool #8815 from the C2 PCM harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (K21) IAT Signal circuit in the IAT Sensor harness connector.

Is there any voltage present?

Yes

- Repair the short to voltage in the (K21) IAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST.Powertrain Verification Test.

No

- Go To 8

8. (K21) IAT SIGNAL CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Measure the resistance between ground and the (K21) IAT Signal circuit in the IAT Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K21) IAT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST.Powertrain Verification Test.

No

- Go To 9

9. (K21) IAT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT




1. Measure the resistance between the (K21) IAT Signal circuit and the (K900) Sensor ground circuit in the IAT Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short between the (K900) Sensor ground circuit and the (K21) IAT Sensor Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 10

10. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the IAT Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Intake Air Temperature Sensor and Powertrain Control Module connectors.
4. Search for any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST.Powertrain Verification Test

No

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST.Powertrain Verification Test

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