Headlamps Inoperative - Low Beams

WARNING: This page is about a different car, the 2007 Hummer H2. 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 Diagnostic System Check - Vehicle?	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	Disconnect the headlamp low relay. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) . Connect a test lamp between the control circuit of the headlamp low relay and the battery positive voltage circuit of the headlamp low relay connector. Does the test lamp illuminate?	Go to Step 14	Go to Step 6
6	Connect the headlamp low relay. Place the headlamp switch in the HEAD position. Disconnect the multifunction switch. Do the low beam headlamps illuminate?	Go to Step 7	Go to Step 10
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 11
9	Inspect for poor connections at the harness connector of the inoperative bulb. Refer to Circuit Testing and Wiring 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 Circuit Testing and Wiring 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 body control module (BCM). Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition?	Go to Step 16	Go to Step 13
12	Replace the inoperative bulb. Refer to Headlamp Replacement or Headlamp Bulb Replacement . 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 low beam headlamp relay. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) . 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