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 Descriptors

DTC P1258
- Engine Coolant Overtemperature - Protection Mode Active

Circuit/System Description

The engine control module (ECM) uses the engine coolant temperature sensor to monitor the engine for an over-temperature condition. This condition occurs when the coolant temperature is above a calibrated value. The ECM will alternately disable 2 groups of 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.

Conditions for Running the DTC

V6

* The engine is operating for 10 seconds or greater.

* DTC P1258 runs continuously once the conditions above have been met.

V8

* The engine is operating for 30 seconds or greater.

* DTC P1258 runs continuously once the conditions above have been met.

Conditions for Setting the DTC

V6

The ECM detects that engine coolant temperature is warmer than 132°C (270°F) for 2 seconds or greater.

V8

The ECM detects that engine coolant temperature is warmer than 129°C (264°F) for 10 seconds or greater.

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 IP will illuminate the coolant temperature indicator lamp and 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 remain active at the start of the next drive cycle until the ECT sensor DTC runs and passes.

Conditions for Clearing the MIL/DTC

DTC P1258 is a Type A DTC.

Reference Information

Description and Operation

* Cooling Fan Description and Operation Cooling Fan

* Instrument Cluster Description and Operation Instrument Cluster

* Indicator/Warning Message Description and Operation Indicator/Warning Message

DTC Type Reference

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

Scan Tool Reference

Engine Control Module Scan Tool Information (LFX) Scan Tool Testing and ProceduresEngine Control Module Scan Tool Information (LS3/L99) Scan Tool Testing and ProceduresEngine Control Module Scan Tool Information (LSA) Scan Tool Testing and Procedures for scan tool information

Circuit/System Verification

Note: If DTC P0480, P0481, P0691, P0692, P0693, or P0694 is set, diagnose that DTC first.

1. Observe the engine coolant level. The engine coolant level should be within the operating range. Refer to Cooling System Draining and Filling (GE 47716) Cooling System Draining and Filling (GE 47716)Cooling System Draining and Filling (LSA, LS3, L99 Static Fill) Cooling System Draining and Filling (Static Fill)Cooling System Draining and Filling (LFX, Static Fill) Cooling System Draining and Filling (Static Fill).

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 (GE 47716) Cooling System Draining and Filling (GE 47716)Cooling System Draining and Filling (LSA, LS3, L99 Static Fill) Cooling System Draining and Filling (Static Fill)Cooling System Draining and Filling (LFX, Static Fill) Cooling System Draining and Filling (Static Fill).

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

* Air flow obstructions or bent fins at the radiator or the A/C condenser-Refer to Symptoms - Engine Cooling Symptoms - Engine Cooling.

Note: A short delay occurs before the ECM changes the cooling fan speed.

4. Command the cooling fans ON and OFF, low and high speed. The engine cooling fans should turn ON and OFF with each command.

• If the cooling fans do not function as indicated, 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 Cleaning and Inspection Water Pump Cleaning and Inspection.

4. Inspect the engine mechanical for worn, leaking, cracked cylinder heads or engine block. Refer to Coolant in Engine Oil Coolant in Engine Oil.

Repair Instructions

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