DTC P0112 Without RPO CTF
Circuit Description
The manifold air temperature (MAT) sensor is a variable resistor, sometimes called a thermistor. The MAT sensor measures the temperature of the air entering the engine. The engine control module (ECM) supplies 5 volts to the MAT signal circuit. When the MAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance lowers. With high sensor resistance, the ECM detects a high voltage on the MAT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the MAT signal circuit. If the ECM detects an excessively low MAT signal voltage, indicating a high temperature, this DTC will set.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The MAT is more than 148°C (298°F) for more than 2 seconds.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
| • | When the vehicle is at ambient temperature the MAT sensor and ECT sensor temperatures should be relatively close to each other. Refer to Temperature Versus Resistance . |
| • | If an intermittent condition is suspected, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |
2 |
Does the temperature measure more than the specified value? | 128°C (262°F) | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC reset? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the MAT sensor temperature measure less than the specified value? | -39°C (-38°F) | Go to Step 6 | Go to Step 5 |
5 | Test the signal circuit of the MAT sensor for a short to ground or a short to MAT low reference circuit and repair as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
6 | Replace the MAT sensor. Did you complete the replacement? | -- | Go to Step 9 | -- |
7 |
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
8 | Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data . Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC run and pass? | -- | Go to Step 10 | Go to Step 2 |
10 | Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
DTC P0112 With RPO CTF
Circuit Description
The intake air temperature (IAT) sensor is a variable resistor, sometimes called a thermistor. The IAT sensor measures the temperature of the air entering the engine. The engine control module (ECM) supplies 5 volts to the IAT signal circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance lowers. With high sensor resistance, the ECM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT signal circuit. If the ECM detects an excessively low IAT signal voltage, indicating a high temperature, DTC P0112 sets.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The battery voltage is between 10-16 volts. |
Conditions for Setting the DTC
The ECM detects that the IAT signal voltage is less than 0.1 volt.
Action Taken When the DTC Sets
| • | The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records. |
| • | The ECM uses an IAT value of -29°C (-20.2°F) for engine starting. |
| • | The ECM uses an IAT value of 25°C (77°F) for engine running. |
| • | The ECM closes the exhaust gas recirculation (EGR) valve and holds to Close position. |
Condition for Clearing the DTC
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
NOTE: The MAF sensor is heated and as a result the IAT sensor may indicate a higher than normal intake air temperature.
| • | When the vehicle is at ambient temperature, the IAT sensor and engine coolant temperature (ECT) sensor temperature should be relatively close to each other. |
| • | Use the Temperature vs. Resistance table to test the IAT sensor at various temperature levels to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns. Refer to Temperature Versus Resistance . |
| • | For intermittent conditions, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||
2 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids | ||||
3 |
Is the IAT Sensor parameter less than the specified value? | -30°C (-22°F) | Go to Step 5 | Go to Step 4 | ||||
4 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 | ||||
5 | Replace the IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- | ||||
6 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 | ||||
7 |
Important: The new ECM must be programmed. Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data . Did you complete the replacement? | -- | Go to Step 8 | -- | ||||
8 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 9 | ||||
9 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
