2010 Cadillac CTS Sedan AWD V6-3.6L Page 847

2010 Cadillac CTS Sedan AWD V6-3.6L Page 847

Conditions for Clearing the MIL/DTC

DTC P0128 is a Type B DTCs.

Diagnostic Aids

An engine that soaks for about 8 hours will help diagnosis the condition. After the cold soak, operate the vehicle at highway speeds for 20 minutes

while monitoring the scan tool Calculated ECT - Thermostat parameter. If there is a condition, the calculated temperature will be 10掳C (18掳F)

warmer than the actual engine coolant temperature.

Reference Information

Schematic Reference

Engine Controls Schematics (LLT) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)Engine Controls Schematics

(LF1) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)

Connector End View Reference

Component Connector End Views (See: Diagrams/Connector Views)

Electrical Information Reference

* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit Testing/Circuit Testing)

* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Connector Repairs/Connector Repairs)

* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit

Testing/Testing for Intermittent Conditions and Poor Connections)

* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Wiring Repairs/Wiring Repairs)

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

1. Verify that the engine coolant level is correct.

瀚慖f the engine coolant is not at the correct level, refer to Loss of Coolant (See: Engine, Cooling and Exhaust/Cooling System/Testing and

Inspection/Symptom Related Diagnostic Procedures/Loss of Coolant).

2. Verify that the engine coolant temperature is at the normal operating temperature.

瀚慖f the engine coolant temperature is colder than the normal operating temperature, refer to Thermostat Diagnosis (LP1, LY7) (See:

Engine, Cooling and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic Procedures/Thermostat Diagnosis

)Thermostat Diagnosis (LS2) (See: Engine, Cooling and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic

Procedures/Thermostat Diagnosis).

3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the

conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B34 ECT sensor.

2. Ignition OFF, remove the fuse that supplies B+ to circuit terminal X2-56 of the K20 ECM.

Caution: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current

draw.

Note: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.

3. Test for less than 5 ohm between the low reference circuit terminal 2 and ground.

瀚慖f greater than specified value, test the circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20

ECM.

4. Install the fuse that supplies B+ to circuit terminal X2-56 of the K20 ECM.

5. Ignition ON, observe the scan tool the ECT sensor parameter. Verify that the ECT sensor parameter is at -40掳C (-40掳F).