P0112-INTAKE AIR TEMPERATURE SENSOR 1 CIRCUIT LOW
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:
With the ignition on and the battery voltage greater than 10.4 Volts.
-
Set Condition:
The Powertrain Control Module (PCM) detects that the Intake Air Temperature (IAT) Sensor input voltage is below the minimum acceptable value.
Possible Causes |
|---|
| (K21) IAT SIGNAL CIRCUIT SHORTED TO GROUND |
| (K21) IAT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT |
| EXCESSIVE RESISTANCE IN THE (K21) IAT SIGNAL CIRCUIT |
| INTAKE AIR TEMPERATURE (IAT) SENSOR |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
1. DIAGNOSTIC TROUBLE CODE (DTC) IS ACTIVE
| 1. | Start the engine and allow it to reach normal operating temperature. |
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.
WARNING:
| 2. | Using the scan tool, select View DTCs. |
Is the status Active for this DTC?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
2. (K21) IAT SIGNAL CIRCUIT SHORTED TO GROUND
 |
| 1. | Turn the ignition off. |
| 2. | Disconnect the Intake Air Temperature Sensor harness connector. |
| 3. | Disconnect the PCM C2 harness connector. |
| 4. | Measure the resistance between ground and the (K21) IAT Signal circuit in the Intake Air Temperature Sensor harness connector. |
Is the resistance above 100 Ohms?
Yes
- Go To 3
No
- Repair the (K21) IAT Signal circuit for a short to ground.
-
Perform the POWERTRAIN
VERIFICATION TEST. (Refer to
28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM)
- Standard
Procedure).
3. (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 above 100 Ohms?
Yes
- Go To 4
No
- Repair the (K21) IAT Signal circuit for a short to the (K900) Sensor Ground circuit.
-
Perform the POWERTRAIN
VERIFICATION TEST. (Refer to
28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM)
- Standard
Procedure).
4. (K21) IAT SIGNAL CIRCUIT HIGH RESISTANCE
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 GPEC Diagnostic Adaptor to perform
the diagnosis.
CAUTION:
| 1. | Connect the Adapter, GPEC Diagnostic 10436 . |
| 2. | Measure the resistance of the (K21) IAT Signal circuit between the IAT Sensor harness connector and the GPEC Adaptor. |
Is the resistance below 5.0 Ohms?
Yes
- Go To 5
No
- Repair the excessive resistance in the (K21) IAT Signal circuit.
-
Perform the POWERTRAIN
VERIFICATION TEST. (Refer to
28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM)
- Standard
Procedure).
5. INTAKE AIR TEMPERATURE SENSOR
| 1. | Turn the ignition off. |
| 2. | Connect the PCM C2 harness connectors. |
| 3. | Turn the ignition on. |
| 4. | Using the scan tool, read the IAT Sensor signal voltage. |
Is the voltage above 4.5 Volts with the Intake Air Temperature Sensor harness disconnected?
Yes
- Replace the Intake Air Temperature Sensor in accordance with the Service Information. (Refer to 14 - Fuel System/Fuel Injection/SENSOR, Air Temperature - Removal) .
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
- Go To 6
6. POWERTRAIN CONTROL MODULE (PCM)
| 1. | Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Intake Air Temperature 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. |
| 4. | Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors. |
| 5. | Look for the data to change or for the DTC to reset during the wiggle test. |
| 6. | Perform any Technical Service Bulletins that may apply. |
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. (Refer to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control - Removal) .
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).