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: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Expose the ambient light sensor to a bright incandescent lamp.
  2. Turn ON the ignition, with the engine OFF.
  3. Place the headlamp switch in the OFF position.
  4. Ensure the parking brake is disengaged.
  5. Block the wheels.
  6. Place the transaxle in NEUTRAL.

Do the daytime running lights (DRL) illuminate?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Using a scan tool, observe the Day/Night Status parameter.

Does the scan tool indicate Day?

Go to Step 6

Go to Step 4

4

  1. Disconnect the ambient light sensor.
  2. Connect a 3-amp fused jumper wire between the ambient light sensor signal circuit and the ambient light sensor low reference circuit.
  3. Using a scan tool, observe the Day/Night Status parameter.

Does the scan tool indicate Day?

Go to Step 7

Go to Step 5

5

Test the ambient light sensor low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 6

6

Inspect for poor connections at the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 8

7

Inspect for poor connections at the ambient light sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 9

8

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 10

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9

Replace the ambient light sensor. Refer to Ambient Light Sensor Replacement .

Did you complete the replacement?

Go to Step 10

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10

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2