P0112

P0112-INTAKE AIR TEMPERATURE SENSOR CIRCUIT LOW

Special Tools:










For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

Intake Air Temperature (IAT) 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.The IAT sensor is a variable resistor that measures the ambient air temperature. The PCM supplies a 5 Volt reference and a ground to the sensors low reference signal circuit. When the IAT is low, the sensor resistance is high. When the IAT is high, the sensor resistance is low.

- When Monitored:
With the ignition on and battery voltage greater than 10.4 Volts.

- Set Condition:
When the Inlet Air Temp Sensor Signal circuit voltage is less than the minimum acceptable value. One trip failure. Three good trips to clear the MIL.





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

1. ACTIVE DTC
1. Start the engine and allow it to reach normal operating temperature.

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.

NOTE: Diagnose and repair any system voltage DTCs before continuing with this test.

2. With the scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. IAT SENSOR
1. Turn the ignition off.
2. Disconnect the IAT Sensor harness connector.
3. Ignition on, engine not running.
4. With the scan tool, read IAT voltage.

NOTE: The sensor voltage should be approximately 5.0 Volts (plus or minus.1 of a Volt) with the connector disconnected.

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 issues were found with the connectors. Service and Repair
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. (K21) IAT SIGNAL CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the C2 PCM harness connector.
3. 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 4

4. (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 5

5. EXCESSIVE RESISTANCE IN THE (K21) IAT SIGNAL CIRCUIT





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 the PCM Pinout Box (8815A) to perform diagnosis.

1. Measure the resistance of the (K21) IAT Signal circuit between the Intake Air Temperature Sensor harness connector and the appropriate terminal of PCM Pinout Box.

Is the resistance below 5.0 Ohms?

Yes

- Go To 6

No

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

6. 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 Sensor and Control Module connectors.
4. Perform 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. PCM/ECM/TCM Reprogramming
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.