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
- Engine Coolant Over-temperature - 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 cylinders, the ECM is able to reduce the temperature of the coolant.


Conditions for Running the DTC

* The engine is running.
* DTCs P0117 or P0118 are not set.



Conditions for Setting the DTC

Coolant temperature more than 139°C (266°F) for more 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, will display a message.



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 (Indicator/Warning Message Description and Operation)
* Audible Warnings Description and Operation (Audible Warnings Description and Operation)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Verification

1. Observe the engine coolant level. The engine coolant level should be within operating range. Refer to Capacities - Approximate Fluid, and Engine Coolant in the Owner's Manual.
2. Ensure that the vehicle has the correct engine coolant, with correct concentration, and is not old, contaminated or contains additives. Refer to Recommended Fluids and Lubricants in the Owner's Manual.
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 Symptoms - Engine Cooling (Symptoms - Engine Cooling) .




Circuit/System Testing

1. Test the thermostat for correct operation. Refer to Thermostat Diagnosis (Thermostat Diagnosis) .
2. Test the engine cooling system for overheating. Refer to Engine Overheating (Engine Overheating) .
3. Inspect the water pump and coolant flow for correct operation. Refer to Water Pump Replacement (With LH8) (Service and Repair)Water Pump Replacement (With LLR) (Service and Repair) .
4. 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) for the 5.3L engine



Repair Instructions

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