2010 Cadillac CTS Sedan AWD V6-3.0L Page 1760

2010 Cadillac CTS Sedan AWD V6-3.0L Page 1760

* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System

Check - Vehicle) prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an

overview of the diagnostic approach.

* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure

Instructions)provides an overview of the diagnostic category.

DTC Descriptor

DTC P1258

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

Conditions for Running the DTC

* The engine is operating for greater than 30 seconds.

* DTC P0116, P0117, P0118, or P0128 is not set.

Conditions for Setting the DTC

* The ECM detects that engine coolant temperature is greater than 136掳C (277掳F) for greater than 1 second or a cumulative time of 10 seconds,

for V6 applications.

* The ECM detects that the engine coolant temperature is greater than 131掳C (267.8掳F) for greater than 7 seconds, for V8 applications.

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 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 System Description and Operation (LF1, LLT) (See: Engine, Cooling and Exhaust/Cooling System/Description and Operation)Cooling

System Description and Operation (LSA) (See: Engine, Cooling and Exhaust/Cooling System/Description and Operation)

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 DTCs P0480, P0481, P0691, P0692, P0693, or P0694 is set, diagnose the DTC first.

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:

* 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 (See: Engine, Cooling

and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic Procedures/Symptoms - Engine Cooling).