Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the low beam headlamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
锟斤拷 If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
锟斤拷 If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the
B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the low beam
headlamp relay.
4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
锟斤拷 If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the appropriate head lamp.
6. Test for less than 5 ohm between the head lamp ground circuit terminal listed below and ground:
* With X88 - Terminal A
* With Z88 - Terminal B
锟斤拷 If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the headlamp.
8. Connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the headlamp is activated.
锟斤拷 If the headlamp does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal,
test or replace the headlamp.
锟斤拷 If the headlamp does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or
replace the headlamp.
9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the Low Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded
states.
锟斤拷 If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
锟斤拷 If 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 BCM.
11. If all circuits test normal, test or replace the low beam headlamp 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))
* Headlamp Replacement (Cadillac Escalade) (See: Lighting and Horns/Headlamp/Service and Repair/Removal and Replacement/Headlamp
Replacement (Cadillac Escalade))Headlamp Replacement (GMC Yukon Two-mode Hybrid) (See: Lighting and Horns/Headlamp/Service
and Repair/Removal and Replacement/Headlamp Replacement (GMC Yukon Two-mode Hybrid))Headlamp Replacement (Yukon) (See:
Lighting and Horns/Headlamp/Service and Repair/Removal and Replacement/Headlamp Replacement (Yukon))Headlamp Replacement
(Chevrolet Tahoe Two-mode Hybrid) (See: Lighting and Horns/Headlamp/Service and Repair/Removal and Replacement/Headlamp
Replacement (Chevrolet Tahoe Two-mode Hybrid))Headlamp Replacement (Tahoe, Avalanche) (See: Lighting and Horns/Headlamp/Service
and Repair/Removal and Replacement/Headlamp Replacement (Tahoe, Avalanche))Headlamp Replacement (Escalade PLATINUM) (See:
Lighting and Horns/Headlamp/Service and Repair/Removal and Replacement/Headlamp Replacement (Escalade Platinum))Headlamp
Replacement (Non HID) (See: Lighting and Horns/Headlamp/Service and Repair/Removal and Replacement/Headlamp Replacement (Non
HID))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for BCM replacement, setup, and programming
