Circuit Description
The engine control module (ECM) 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 131°C (268°F). When an over temperature condition is present, DTC P1258 will set. The ECM will disable 2 groups of 4 cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the ECM 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 ECM detects an ECT over 131°C (268°F). |
| • | The above condition is present for at least 3 seconds. |
Action Taken When the DTC Sets
| • | The ECM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed. |
| • | The ECM will signal the instrument panel cluster (IPC) to turn ON the Service Engine Soon indicator. |
| • | The ECM will alternately disable 2 groups of 4 cylinders by turning OFF the fuel injectors. |
| • | The ECM will store conditions which were present when the DTC set in Freeze Frame Data. |
| • | The ECM will command the fan on high speed. |
Conditions for Clearing the MIL/DTC
| • | The ECM will turn the MIL OFF after 4 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 | |
2 | Inspect the engine cooling fans for proper operation. Are the engine cooling fans operative? | Go to Engine Overheating | |
