Circuit Description
The engine control module (ECM) uses the 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 engine coolant temperature 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 IPC to turn ON the Service Engine Soon indicator. |
| • | The ECM will alternately disable two groups of four cylinders by turning OFF the fuel injectors. |
| • | The ECM will store conditions which were present when the DTC set in Freeze Frame Data. |
| • | 90 percent fan power is commanded. |
Conditions for Clearing the MIL/DTC
| • | The ECM 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 | Inspect the engine cooling fan for proper operation. Is the engine cooling fan operative? | Go to Engine Overheating | Go to Cooling Fan Always On |
