Low and High Beams Headlamps Inoperative. GMC Truck GMC C-Series Medium Duty Truck B7 2001

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C-Series Medium Duty Truck B7 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Low and High Beams Headlamps Inoperative

Step	Action	Yes	No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
1	Did you review the headlamps description and operation and perform the necessary inspections?	Go to Step 2	Go to Symptoms - Lighting Systems
2	Place the headlamp switch in the HEADLAMP position. Place the headlamp dimmer switch in the HIGH position. Place the headlamp dimmer switch in the LOW position. Do the headlamps illuminate in both headlamp dimmer switch positions?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Do the headlamps illuminate in only the HIGH or LOW headlamp dimmer switch positions?	Go to Headlamps Inoperative - High Beams or Headlamps Inoperative - Low Beams	Go to Step 4
4	Place the headlamp switch in the OFF position. Disconnect the headlamp dimmer switch. Probe the headlamp switch signal circuit with a test lamp that is connected to a good ground. Place the headlamp switch in the HEADLAMPS ON position. Does the test lamp illuminate?	Go to Step 7	Go to Step 5
5	Test the headlamp switch signal circuit for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 10	Go to Step 6
6	Inspect for poor connections at the harness connector of the headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 10	Go to Step 9
7	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 in Wiring Systems. Did you find and correct the condition?	Go to Step 10	Go to Step 8
8	Replace the headlamp dimmer switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column-Standard. Did you complete the replacement?	Go to Step 10	--
9	Replace the headlamp switch. Refer to Headlamp Switch Replacement . Did you complete the replacement?	Go to Step 10	--
10	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 3