2010 Cadillac CTS Sedan AWD V6-3.6L Page 1057
P0128
* The ECM detects that the actual engine coolant temperature is 11掳C (20掳F) colder than the calculated thermostat regulating temperature of 89
掳C (192掳F), for greater than 4 s or for a cumulative of 30 s.
OR
* The ECM detects that the actual engine coolant temperature is 10掳C (18掳F) colder than the calculated ECT for greater than 1 s or a
cumulative of 10 s.
Action Taken When the DTC Sets
DTC P0128 is a Type B DTCs.
Conditions for Clearing the MIL/DTC
DTC P0128 is a Type B DTCs.
Diagnostic Aids
An engine that soaks for about 8 h will help diagnosis the condition. After the cold soak, operate the vehicle at highway speeds for 20 min 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.
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
