Headlamps Inoperative - Low Beams

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

Headlamps Inoperative - Low Beams Diagnostic Test

Step	Action	Yes	No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Lighting Systems Connector End Views or Body Control System Connector End Views in Body Control System or Wiper/Washer System Connector End Views in Wiper/Washer Systems
1	Did you perform the Lighting Systems Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Lighting Systems
2	Verify that the low beam headlamps are inoperative. Do the low beam headlamps operate normally?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Is only one low beam headlamp inoperative?	Go to Step 4	Go to Step 5
4	Inspect the inoperative bulb for an open filament and connector for poor terminal contact and replace/repair as necessary. Refer to Headlamp Bulb Replacement (TrailBlazer) Headlamp Bulb Replacement (Bravada, Envoy, Envoy XUV, Rainier) or Wiring Repairs in Wiring Systems. If no problem is found, repair the open, high resistance or short to ground in the low beam headlamp supply voltage circuit or ground circuit to the inoperative lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 19	-
5	Does the wiper activated headlamp (WAH) function of the wiper system operate normally?	Go to Step 8	Go to Step 6
6	Block the wheels. Place the ignition switch in the RUN position with the engine OFF. Place the gearshift lever in DRIVE. Place the wiper switch in the LO speed position. Use the scan tool to monitor the Front Wipers Active input to the BCM. Does the scan tool display Yes after approximately 3 cycles of the wiper blades?	Go to Step 14	Go to Step 7
7	Test the windshield wiper switch signal 2 circuit for an open, high resistance, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition?	Go to Step 19	Go to Step 13
8	Test the headlamp switch signal and ground circuits for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition?	Go to Step 19	Go to Step 9
9	Place the headlamp switch in the HEAD position. Connect a fused jumper from ground to the headlamp switch signal terminal of the headlamp switch connector. Do the low beam headlamps illuminate?	Go to Step 12	Go to Step 10
10	Connect a fused jumper from ground to the headlamp driver module control circuit terminal at the headlamp driver module (HDM) in the underhood fuse block. Do the low beam headlamps illuminate?	Go to Step 14	Go to Step 11
11	Test the headlamp driver module ground circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition?	Go to Step 19	Go to Step 17
12	Inspect for poor connections at the harness connector of the headlamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 19	Go to Step 18
13	Inspect for poor connections at the harness connector of the wiper motor cover. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 19	Go to Step 15
14	Inspect for poor connections at the harness connector of the Body Control Module (BCM). Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 19	Go to Step 16
15	Replace the wiper motor cover. Refer to Wiper Motor Cover Replacement in Wipers/Washers Systems. Did you complete the repair?	Go to Step 19	-
16	IMPORTANT: Perform the setup procedure for the BCM. Replace the body control module (BCM). Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?	Go to Step 19	-
17	Replace the headlamp driver module (HDM). Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the repair?	Go to Step 19	-
18	Replace the headlamp switch. Refer to Headlamp Switch Replacement . Did you complete the repair?	Go to Step 19	-
19	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 3