2010 Cadillac Truck SRX AWD V6-2.8L Turbo Page 1087
Circuit Description
The engine control module (ECM) monitors the temperature of the engine coolant for engine control and as an enabling criteria for some
diagnostics. The amount of air flow into an engine is proportional to the amount of heat an engine generates. The ECM monitors the amount of air
flow into the engine to calculate engine coolant temperature (ECT). The ECM uses the calculated temperature to determine if the engine has
warmed up to the closed loop temperature or to the thermostat regulating temperature. If the coolant temperature does not increase normally or does
not reach the closed loop temperature, diagnostics that use the ECT as enabling criteria, may not run when expected.
Conditions for Running the DTC
P0128
* Before the ECM can report DTC P0128 failed, DTC P0117 and P0118 must run and pass.
* DTCs P0100, P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117, P0118, P0119, or P0700 is not set.
* The engine speed is greater than 960 RPM.
* The ECT is colder than 51掳C (124掳F) at start up.
* The vehicle speed is greater than 8 km/h (5 mph).
* The air flow coming into the engine has accumulated to greater than 3,459 grams.
* DTC P0128 runs continuously once the above conditions have been met for approximately 15 min.
OR
* DTCs P0116, P0117, P0118, or P0119 is not set.
* The engine speed is greater than 25 RPM.
* The block heater is not detected.
* DTC P0128 runs continuously once the above conditions have been met for approximately 8 min.
Conditions for Setting the DTC
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 (LAU) (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/Connector End Views By Name)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (See: Diagnostic Trouble Code Descriptions/Powertrain Diagnostic Trouble Code
