Circuit Description
The powertrain control module (PCM) uses the engine coolant temperature (ECT) sensor to monitor the engine for an over temperature condition. This condition occurs when the coolant temperature is above 128°C (262°F). When an over temperature condition is present, DTC P1258 will set. The PCM will disable 2 groups of cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the PCM is able to reduce the temperature of the coolant.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1258 Engine Coolant Overtemperature - Protection Mode Active
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The PCM detects an engine metal over temperature. |
| • | The above condition is present for at least 8 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator Lamp (MIL) during the first trip in which the diagnostic test has been run and failed. |
| • | The PCM will signal the instrument panel cluster (IPC) to turn ON the Service Engine Soon indicator. |
| • | The PCM will alternately disable 2 groups of cylinders by turning OFF the fuel injectors. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. |
| • | A history DTC is stored. |
| • | The driver information center (DIC), if equipped may display a message. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after 3 consecutive trips that the diagnostic has been run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear DTC Information function. |
Step | Action | Yes | No |
|---|---|---|---|
Connector End View Reference: Cooling System Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Check the engine cooling fans for proper operation. Are the engine cooling fans operative? | Go to Engine Overheating | |
