Headlamps Inoperative - Low Beams (Standard)

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

Step	Action	Yes	No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views
1	Did you perform the Lighting Systems Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Place the headlamp switch in the ON position. Place the dimmer switch in the low beam position. Do the low beam headlamps operate normally?	Go to Testing for Intermittent Conditions and Poor Connections	Go to Step 3
3	Is only one low beam headlamp inoperative?	Go to Step 4	Go to Step 5
4	Test the headlamp low beam supply voltage and ground circuits for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 16	Go to Step 9
5	Place the headlamp switch in the HEAD position. Place the headlamp dimmer switch in the low beam position. With a scan tool, monitor the Low Beam Relay Command data parameter in the body control module (BCM) data list. Does the scan tool display On?	Go to Step 14	Go to Step 6
6	Disconnect the multifunction switch. Do the low beam headlamps illuminate?	Go to Step 7	Go to Step 11
7	Test the headlamp dimmer switch signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct a condition?	Go to Step 16	Go to Step 8
8	Test the headlamp switch flash to pass signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct a condition?	Go to Step 16	Go to Step 10
9	Inspect for poor connections at the harness connector of the inoperative bulb. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	Go to Step 16	Go to Step 12
10	Inspect for poor connections at the harness connector of the headlamp dimmer switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	Go to Step 16	Go to Step 15
11	Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	Go to Step 16	Go to Step 13
12	Replace the inoperative bulb. Refer to Headlamp Bulb Replacement (Cadillac) or Headlamp Bulb Replacement (Tahoe, Avalanche) or Headlamp Bulb Replacement (Yukon) . Did you complete the replacement?	Go to Step 16	-
13	Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	Go to Step 16	-
14	Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement . Did you complete the replacement?	Go to Step 16	-
15	Replace the headlamp dimmer switch. Refer to Turn Signal Multifunction Switch Replacement . Did you complete the repair?	Go to Step 16	-
16	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 3