GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

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 in Vehicle DTC Information

2

  1. Ensure that the ambient light sensor is receiving enough light to simulate daylight conditions.
  2. Place the headlamp switch in the OFF position.
  3. Turn ON the ignition, with the engine OFF.
  4. Turn OFF the ignition.

Do the headlamps operate normally?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Are the headlamps ON with the ignition key ON, and then turn OFF when the ignition key is placed in the OFF position?

Go to Step 4

Go to Step 5

4

Test the headlamp relay control circuit of the body control module (BCM) for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 10

5

Disconnect the headlamp relay. Refer to Relay Replacement in Wiring Systems.

Do the headlamps turn OFF?

Go to Step 8

Go to Step 6

6

Disconnect the headlamp switch connector.

Do the headlamps turn OFF?

Go to Step 7

Go to Step 11

7

Test the headlamp relay output circuit of the headlamp relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 9

8

Inspect for poor connections at the harness connector of the headlamp relay. 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 15

Go to Step 12

9

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 15

Go to Step 13

10

Inspect for poor connections at the harness connector of the BCM. 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 15

Go to Step 14

11

Repair the short to ground in the headlamp low or high beam signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct a condition?

Go to Step 15

--

12

Replace the high beam headlamp relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the repair?

Go to Step 15

--

13

Replace the headlamp switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the repair?

Go to Step 15

--

14

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 15

--

15

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3