GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

Schematic Reference: Headlights Schematics

1

Did you perform the Lighting Systems Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Turn the headlamp switch to the OFF position.
  2. Turn ON the ignition, with the engine OFF.
  3. Cover and uncover the ambient light sensor.

Does the system operate normally?

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Go to Testing for Electrical Intermittents in Wiring Systems

Go to Step 3

3

  1. Turn ON the ignition with the engine OFF.
  2. With the scan tool, read the ambient light sensor voltage in the BCM.
  3. While monitoring the scan tool, cover the ambient light sensor, then induce a light source to the sensor.

Does the sensor voltage vary near the specified values?

Above 2.2 V, Below 1.3 V

Go to Step 4

Go to Step 10

4

Disconnect the headlamp relay.

Are the headlamps illuminated?

--

Go to Step 12

Go to Step 5

5

  1. Reconnect the headlamp relay.
  2. Disconnect the headlamp and panel dimmer switch connector.

Are the headlamps illuminated?

--

Go to Step 6

Go to Step 9

6

Disconnect the BCM connector C2.

Are the headlamps illuminated?

--

Go to Step 7

Go to Step 11

7

Test the headlamp relay coil supply voltage circuit of the headlamp relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 17

Go to Step 8

8

Inspect for poor connections at 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 17

Go to Step 13

9

Inspect for poor connections at the headlamp and panel 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 17

Go to Step 14

10

Inspect for poor connections at the ambient light sensor. 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 17

Go to Step 15

11

Inspect for poor connections at 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 17

Go to Step 4

12

Repair the short to voltage in the battery positive voltage circuit between the headlamp relay and the headlamps. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 17

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13

Replace the headlamp relay.

Did you complete the replacement?

--

Go to Step 17

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14

Replace the headlamp and panel dimmer switch. Refer to Headlamp Switch Replacement .

Did you complete the replacement?

--

Go to Step 17

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15

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

Did you complete the replacement?

--

Go to Step 17

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16

Important: Perform the setup procedure for the BCM.

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

--

Go to Step 17

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17

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3