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 132°C (270°F). When an over temperature condition is present, DTC P1258 will set. The PCM will disable 2 groups of 4 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
| • | DTCs P0117, P0118, P1114, and P1115 are not active. |
| • | The engine is running. |
Conditions for Setting the DTC
The engine coolant temperature is above 132°C (270°F) for 10 seconds or more.
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 4 cylinders by turning OFF the fuel injectors. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
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 |
|---|---|---|---|
1 | Was the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Check the engine cooling fan for proper operation. Is the engine cooling fan operative? | Go to Engine Overheating |
