DTC P1258 Engine Coolant Overtemperature - Protection Mode Active. Cadillac Concours 1996

For 1990-2009 cars
Engine Controls Components
IAT/ ECT/ TP/ MAP and BBV Sensors
OBD II Symbol Description Notice
ESD Notice
ESD Notice

### Circuit Description

The PCM has the ability to disable 4 injectors during an engine over temperature condition. The engine is considered over temperature whenever the ECT reaches 131°C (268°F). This protection mode permits the PCM to alternate between groups of cylinders, thereby reducing coolant temperature. This is accomplished by disabling the fuel injectors. This DTC is set to show that an overtemperature condition was or is observed by the PCM and that the protection mode has been engaged.

### Conditions for Setting the DTC

#### Test Condition

Always tested.

#### Failure Condition

When the protection mode has been engaged by the PCM.

### Action Taken When the DTC Sets

• | PCM turns ON the SERVICE ENGINE COOLING SYSTEM message.

• | Engine operates in alternating 4 cylinder mode.

• | The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

• | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

• | A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.

• | Use a scan tool to clear DTCs.

• | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. An ECT sensor or circuit malfunction may falsely engage the protection mode or there is a cooling system problem.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to A Powertrain On Board Diagnostic (OBD) System Check
2 | Is DTC P0118 or P1114 also set? | -- | Go to DTCs that are set | Go to cooling system diagnosis