2010 Cadillac Truck Escalade/ESV RWD V8-6.2L Page 2207
瀚慖f the test lamp does not illuminate, test the ignition circuit for a short to ground or a open/high resistance. If the circuit tests normal and
ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
4. Verify that a test lamp illuminates between the relay B+ circuit terminal 30 and ground.
瀚慖f the test lamp does not illuminate, test the B+ circuit for a short to ground or a open/high resistance. If the circuit tests normal and B+
circuit fuse is open, replace the A/C clutch relay.
5. Disconnect the harness connector at the A/C clutch coil.
6. Test for less than 1 ohm between the ground circuit terminal 2 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 A/C clutch coil.
8. Connect a 10-amp fused jumper wire between the B+ circuit terminal 30 and control circuit terminal 87. Verify the A/C clutch is activated.
瀚慖f the A/C clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C
clutch.
9. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
10. Command the A/C relay output function 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 control circuit for a short to ground. If the circuit tests normal, replace the ECM.
瀚慖f the test lamp is always OFF, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace
the ECM.
11. If all circuits test normal, test or replace the A/C clutch relay.
Component Testing
1. Ignition OFF, disconnect the A/C COMP relay.
2. Test for 60-180 ohms between terminals 85 and 86.
瀚慖f the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
瀚慖f not the specified value, replace the relay.
4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test
for less than 2 ohms between terminals 30 and 87.
瀚慖f greater than the specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (See: Power and Ground Distribution/Power Distribution Relay/Service and Repair/Relay
Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (See: Power and Ground Distribution/Power
Distribution Relay/Service and Repair/Relay Replacement (Within an Electrical Center))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for ECM replacement, setup, and programming
HVAC - Automatic
DTC P0645
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.
