2010 Cadillac Truck Escalade/ESV RWD V8-6.2L Page 2429
DTC P1258 is a Type A DTC.
Reference Information
Description and Operation
* Cooling System Description and Operation (See: Engine, Cooling and Exhaust/Cooling System/Description and Operation/Cooling System
Description and Operation)
* Instrument Cluster Description and Operation (See: Instrument Panel, Gauges and Warning Indicators/Description and
Operation/Instrument Cluster)
* Indicator/Warning Message Description and Operation (See: Instrument Panel, Gauges and Warning Indicators/Description and
Operation/Indicator/Warning Message)
* Audible Warnings Description and Operation (See: Instrument Panel, Gauges and Warning Indicators/Description and Operation/Audible
Warnings)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (See: Diagnostic Trouble Code Descriptions/Powertrain Diagnostic Trouble Code
(DTC) Type Definitions)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Note: If DTC P0480, P0481, or P0482 is set, diagnose that DTC first.
1. Observe the engine coolant level. The engine coolant level should be within operating range. Refer to Cooling System Draining and Filling
(Static Fill) (See: Engine, Cooling and Exhaust/Cooling System/Service and Repair/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 (Static Fill) (See: Engine, Cooling and Exhaust/Cooling System/Service and Repair/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
* The radiator and A/C condenser for any air flow obstructions or bent fins-Refer to Symptoms - Engine Cooling (See: Engine, Cooling
and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic Procedures/Symptoms - Engine Cooling).
Note: A small delay occurs before the ECM changes the cooling fan speed.
4. Command the cooling fans ON in each available speed with a scan tool.
瀚慖f the cooling fans are inoperative in any of the commanded states, refer to Cooling Fan Inoperative (without HP2) (See: Engine,
Cooling and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic Procedures/Cooling Fan Inoperative)Cooling
Fan Inoperative (with HP2) (See: Engine, Cooling and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic
Procedures/Cooling Fan Inoperative).
Circuit/System Testing
1. Test the thermostat for correct operation. Refer to Thermostat Diagnosis (See: Engine, Cooling and Exhaust/Cooling System/Testing and
Inspection/Symptom Related Diagnostic Procedures/Thermostat Diagnosis).
2. Test the engine cooling system for overheating. Refer to Engine Overheating (See: Engine, Cooling and Exhaust/Cooling System/Testing
and Inspection/Symptom Related Diagnostic Procedures/Engine Overheating).
3. Inspect the water pump and coolant flow for correct operation. Refer to Water Pump Replacement (See: Engine, Cooling and
Exhaust/Cooling System/Water Pump/Service and Repair).
4. Inspect the engine for worn/leaking/cracked cylinder heads and engine block. Refer to Coolant in Combustion Chamber (See: Engine,
Cooling and Exhaust/Engine/Testing and Inspection/Symptom Related Diagnostic Procedures/Coolant in Combustion Chamber) and Coolant
in Engine Oil (See: Engine, Cooling and Exhaust/Engine/Testing and Inspection/Symptom Related Diagnostic Procedures/Coolant in
Engine Oil).
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
