GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Body 🢒 Lighting Systems 🢒 Headlamps Inoperative - Low Beams

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference: Master Electrical Component List

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 HEADLAMP position.

Do the low beam headlamps illuminate?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3
  1. Turn ON the ignition, with the engine OFF.
  2. Place the headlamp switch in the OFF position.
  3. Disengage the parking brake.

Are the daytime running lamps (DRL) ON?

Go to Step 4

Go to Daytime Running Lamps (DRL) Inoperative

4
  1. Turn OFF the ignition.
  2. Remove the DRL relay.
  3. Probe the headlamp dimmer switch headlamp low beam supply voltage circuit at the DRL relay with a test lamp that is connected to a good ground.
  4. Place the headlamp switch in the HEADLAMP position.
  5. Place the headlamp dimmer switch in the LOW position.

Does the test lamp illuminate?

Go to Step 6

Go to Step 5

5
  1. Place the headlamp switch in the OFF position.
  2. Disconnect the turn signal/multifunction switch.
  3. With the test lamp still connected, connect a 10-amp fused jumper wire between the headlamp switch signal circuit of the turn signal/multifunction switch and the headlamp low beam supply voltage circuit of the turn signal/multifunction switch.

Does the test lamp illuminate?

Go to Step 7

Go to Step 8

6

Inspect for poor connections at the DRL relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

Inspect for poor connections at the harness connector of the turn signal/multifunction switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Repair the following in the headlamp low beam supply voltage circuit:

    • An open
    • A high resistance
    • A short to ground

Refer to Circuit Testing or Wiring Repairs .

Did you complete the repair?

Go to Step 11

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9

Replace the DRL relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 11

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10

Replace the turn signal/multifunction switch. Refer to Turn Signal Multifunction Switch Replacement .

Did you complete the replacement?

Go to Step 11

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11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3