P1258

DTC P1258

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P1258

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Engine Coolant Overtemperature - Protection Mode Active

Circuit/System 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 a calibrated value for a calibrated length of time. The ECM will disable half of the cylinders by turning OFF the fuel injectors. By disabling half of the cylinders, the ECM is able to reduce the temperature of the coolant.

Conditions for Running the DTC

The engine is operating.

Conditions for Setting the DTC

The coolant temperature is warmer than 129°C (264°F) for greater than 10 seconds.

Action Taken When the DTC Sets

* DTC P1258 is a Type A DTC.

* The engine will operate in the Overheated Engine Protection Operating Mode.

* The engine coolant temperature indicator lamp, if equipped, will illuminate.

* The driver information center (DIC), if equipped, may display a message.

* If the protection mode is active and an ECT sensor DTC sets, the protection mode will activate during the next drive cycle until the ECT sensor DTC runs and passes.

Conditions for Clearing the DTC

DTC P1258 is a Type A DTC.

Reference Information

Description and Operation

* Cooling System Description and Operation Description and Operation

* Instrument Cluster Description and Operation Description and Operation

* Indicator/Warning Message Description and Operation Description and Operation

* Audible Warnings Description and Operation Description and Operation

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Observe the engine coolant level. The engine coolant level should be within operating range. Refer to Cooling System Draining and Filling (Static Fill) Cooling System Draining and Filling (Static Fill)Cooling System Draining and Filling (Vac N Fill) Cooling System Draining and Filling (Vac N Fill)Cooling System Draining and Filling (Static Fill Diesel) Cooling System Draining and Filling (Static Fill Diesel).

2. Ensure that the vehicle has the correct engine coolant, with correct concentration, and is not old, contaminated or contains additives. Refer to Cooling System Draining and Filling (Static Fill) Cooling System Draining and Filling (Static Fill)Cooling System Draining and Filling (Vac N Fill) Cooling System Draining and Filling (Vac N Fill)Cooling System Draining and Filling (Static Fill Diesel) Cooling System Draining and Filling (Static Fill Diesel).

3. Inspect the cooling system for the following:

* Leaks

* Kinked or pinched hoses, especially at the radiator

* Loose, missing, or damaged radiator air seals or deflectors

* The radiator and A/C condenser for any air flow obstructions or bent fins. Refer to Engine Overheating Engine Overheating.

Circuit/System Testing

1. Test the thermostat for correct operation. Refer to Thermostat Diagnosis Thermostat Diagnosis.

2. Test the fan clutch for proper operation. Refer to Fan Clutch Diagnosis Testing and Inspection.

3. Test the engine cooling system for overheating. Refer to Engine Overheating Engine Overheating.

4. Inspect the water pump and coolant flow for correct operation. Refer to Water Pump Replacement (V6) Service and RepairWater Pump Replacement (V8) Service and RepairWater Pump Replacement (LMF/LY2) Service and RepairWater Pump Replacement (Diesel) Service and Repair.

5. Inspect the engine for worn/leaking/cracked cylinder heads and engine block. Refer to Coolant in Combustion Chamber Coolant in Combustion Chamber and Coolant in Engine Oil Coolant in Engine Oil.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.