2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 780
The primary purpose of the heater core coolant pump is to circulate engine coolant through the HVAC heater core when heat is required in the
cabin for comfort. This normally happens when the vehicle is in an Auto Stop and the mechanical pump is not spinning. If the HVAC control
module has determined heat is needed for the cabin, this pump is turned on once the engine is shut off so the customer does not notice a change in
heater duct discharge temperatures. The HVAC control module controls the auxiliary coolant pump relay via the heater core coolant pump relay
control circuit. Heater core coolant pump relay supplies voltage to the heater core coolant pump.
Conditions for Running the DTC
* The ignition is ON.
* Ignition voltage is between 9-16 volts.
* The HVAC module is ON.
Conditions for Setting the DTC
Control circuit over current
Action Taken When the DTC Sets
Set heater core pump validity to invalid.
Conditions for Clearing the DTC
* Over current fault removed.
* Clears 30 seconds after cycle wake up signal.
* Open fault removed.
* Normal range for 3.5 seconds.
Reference Information
Schematic Reference
Hybrid Cooling Schematics ()
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Air Delivery Description and Operation (See: Heating and Air Conditioning/Description and Operation/HVAC - Automatic/Air Delivery
Description and Operation)
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)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, command the heater core pump ON and OFF with a scan tool.
2. Observe the operation of heater core pump.
Circuit/System Testing
1. Disconnect the heater core coolant pump relay.
2. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit terminal 87 and ground.
瀚慖f the test lamp illuminates, test the relay controlled output circuit for a short to voltage.
3. Verify that a test lamp illuminates between the relay coil B+ circuit terminal 85 and ground.
瀚慖f the test lamp does not illuminate, test the relay coil B+ circuit for a short to ground or an open/high resistance. If the circuit tests
normal and the relay coil B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal,
