P0111
P0111-INTAKE AIR TEMPERATURE SENSOR RATIONALITY
For a complete wiring diagram refer to Diagrams/Electrical.
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.
- When Monitored:
The engine off time is greater than 480 minutes. Ambient Temperature if greater than 4° C (38° F).
- Set Condition:
After a calibrated amount of cool down time the PCM 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
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. INTAKE 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 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
No
- Go To 3
3. IAT SENSOR VOLTAGE
Turn the ignition off.
Disconnect the Intake Air Temperature Sensor harness connector.
Turn the ignition on.
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
Turn the ignition off.
Connect a jumper wire between the (K21) IAT Signal circuit and the (K900) Sensor ground circuit in the IAT Sensor harness connector.
Turn the ignition on.
With a scan tool, read the IAT 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 IAT Sensor.
- 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
Turn the ignition off.
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 Miller Special Tool #8815 and #8815-1 to perform diagnosis.
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 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 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
Turn the ignition off.
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 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 open in the (K900) Sensor ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
7. PCM
NOTE: Before continuing, check the PCM 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 the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test