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 Overtemperature - Protection Mode Active
Circuit/System Description
The engine control module (ECM) or powertrain control module (PCM) uses the engine coolant temperature (ECT) sensor to monitor the engine for an overtemperature condition. This condition occurs when the coolant temperature is above a calibrated value for a calibrated length of time. The ECM or PCM will disable half of the cylinders by turning OFF the fuel injectors. By disabling half of cylinders, the ECM or PCM is able to reduce the temperature of the coolant.
Conditions for Running the DTC
* The engine is running.
* DTC P0116, P0117, P0118, or P0128 are not set.
Conditions for Setting the DTC
Coolant temperature more than 131°C (267.8°F) for more than 7 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 instrument panel (IP) will illuminate the coolant temperature indicator lamp and the driver information center (DIC), if equipped, may display a message.
Conditions for Clearing the DTC
DTC P1258 is a Type A DTC.
Reference Information
Description and Operation
* Cooling Fan Description and Operation (Cooling Fan Description and Operation)
* Instrument Cluster Description and Operation (Instrument Cluster)
* Indicator/Warning Message Description and Operation (Indicator/Warning Message)
* Audible Warnings Description and Operation (Audible Warnings)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning)for scan tool information
Circuit/System Verification
Important: If DTC P1428 is set, diagnose that DTC first.
1. Observe the engine coolant level. The engine coolant level should be within operating range.
2. Ensure that the vehicle has the correct engine coolant, with correct concentration, and is not old, contaminated or contains additives.
3. Inspect the cooling system for the following:
* Cooling system 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).
Important: A small delay occurs before the ECM changes the cooling fan speed.
4. Command the cooling fans in both low and high speed.
• If the cooling fans do not operate in both speeds, refer to Cooling Fan Inoperative (Cooling Fan Inoperative).
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 (LZ9 or LGD) (Service and Repair)Water Pump Replacement (LD8) (Service and Repair).
4. Inspect the engine mechanical for worn/leaking/cracked cylinder heads and engine block. Refer to Coolant in Combustion Chamber (Coolant in Combustion Chamber).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.