GM Service Manual Online
For 1990-2009 cars only

Step

Action

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

Connector End View Reference: Lighting Systems Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Place the headlamp switch in the HEADLAMP position.
  2. Place the headlamp dimmer switch in the HIGH position.

Do the high beam headlamps illuminate?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

  1. Disconnect the lighting high low relay.
  2. Probe the switch side high beam voltage input circuit of the lighting high low relay with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

4

Connect a fused jumper wire between the switch side high beam voltage supply circuit and the switch side output circuit of the lighting high low relay.

Do the high beam headlamps illuminate?

Go to Step 5

Go to Step 11

5

Probe the coil side voltage supply circuit of the lighting high low relay with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 12

6

Connect a test lamp between the coil side voltage supply circuit and the coil side control circuit of the lighting high low relay.

Does the test lamp illuminate?

Go to Step 8

Go to Step 7

7

  1. Connect a fused jumper wire between the coil side voltage supply circuit and the coil side control circuit of the lighting high low relay.
  2. Place the headlamp switch in the OFF position.
  3. Disconnect the multifunction switch.
  4. Probe the coil side control circuit of the lighting relay at the multifunction switch with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 13

8

Inspect for poor connections at the lighting high low relay. 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 14

9

Inspect for poor connections at the multifunction 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

10

Repair an open or high resistance in the switch side high beam voltage input circuit of the lighting high low relay. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 16

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11

Repair an open or high resistance in the switch side output circuit of the lighting high low relay. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 16

--

12

Repair an open or high resistance in the coil side voltage supply circuit of the lighting high low relay. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 16

--

13

Repair an open or high resistance in the coil side control circuit of the lighting high low relay. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 16

--

14

Replace the lighting high low relay.

Did you complete the replacement?

Go to Step 16

--

15

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

Did you complete the replacement?

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