Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics (See: Diagrams/Electrical Diagrams/Lighting and Horns/System
Diagram/Headlights/Daytime Running Lights (DRL) Schematics)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems 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 Testing
Warning
The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:
* Never open the high intensity discharge system ballast or the arc tube assembly starter.
* Never probe between the high intensity discharge system ballast output connector and the arc tube assembly.
1. Ignition OFF, disconnect the X4 harness connector at the fuse block - underhood.
2. Connect a test lamp between the control circuit terminal H4 and B+.
3. Command the DRLs 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.
4. Ignition OFF, connect the X4 harness connector at the fuse block - underhood. Disconnect the harness connector at the daytime running lamp.
5. Test for less than 5 ohm between the daytime running lamp ground circuit terminal listed below and ground:
* With X88 - Terminal C
* With Z75 and Z88 - Terminal B
锟斤拷 If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between control circuit terminal A and ground:
7. Command the DRLs 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 voltage. If the circuit tests normal, replace the fuse block - underhood.
锟斤拷 If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal,
test or replace the fuse block - underhood.
锟斤拷 If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or
replace the daytime running lamp.
8. If all circuits test normal, test or replace the daytime running lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* 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
