2010 Cadillac Truck Escalade RWD V8-6.0L Hybrid Page 738
test or replace the heater core coolant pump relay.
4. Verify that a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.
瀚慖f the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the heater core coolant pump.
6. Test for less than 5.0 ohms between the heater core coolant pump ground circuit terminal and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the heater core coolant pump.
8. Connect a 15 A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay controlled output circuit terminal 87. Verify
the heater core coolant pump is activated.
瀚慖f the heater core coolant pump does not activate, test the relay controlled output circuit for an open/high resistance. If the circuit tests
normal, test or replace the heater core coolant pump.
9. Connect a test lamp between the relay coil B+ circuit terminal 85 and the relay coil control circuit terminal 86.
10. Command the heater core coolant pump on and off with a scan tool. The test lamp should turn ON and OFF when changing between the
commanded states.
瀚慖f the test lamp is always ON, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the HVAC control
module.
瀚慖f the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If the circuit tests
normal, replace the HVAC control module.
11. If all circuits test normal, test or replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Control Module References (See: Testing and Inspection/Programming and Relearning) for HVAC control module replacement, setup, and
programming
* Heater Coolant Pump Replacement (HP2) (See: Engine, Cooling and Exhaust/Cooling System/Auxiliary Water Pump/Service and Repair)
B3873
DTC B3873
Diagnostic Instructions
* 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 each diagnostic category.
DTC Descriptor
DTC B3873 00
- Front Washer Relay Circuit
Diagnostic Fault Information
