GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

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

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Place the ignition switch in the OFF position.
  2. Engage the parking brake.
  3. Place the headlamp switch in the HEAD position.
  4. Place the headlamp switch in the OFF position.
  5. Turn ON the ignition, with the engine OFF.
  6. Place the turn signal switch in the RH ON position.
  7. Place the turn signal switch in the LH ON position.

Do the front turn signals illuminate?

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Go to Step 3

Go to Turn Signal Lamps and/or Indicators Inoperative

3

  1. Place the turn signal switch in the OFF position.
  2. Disengaged the parking brake.
  3. Expose the ambient light sensor to a bright incandescent lamp.
  4. Wait more than 20 seconds.

Do the front turn signal lamps illuminate?

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

Go to Step 4

4

Are the automatic headlamps illuminated?

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Go to Step 5

Go to Step 6

5

  1. Install the scan tool.
  2. Expose the ambient light sensor to a bright incandescent lamp.
  3. Wait more than 20 seconds.
  4. With a scan tool, observe the Ambient Light Sensor parameter in the Body Control Module (BCM) data list.

Does the scan tool indicate that the Ambient Light Sensor Input parameter is within the specified range?

0.25-2.5 V

Go to Step 14

Go to Step 11

6

Is the park brake indicator in the instrument panel cluster (IPC) ON?

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Go to Brake Warning Indicator Always On in Hydraulic Brakes

Go to Step 7

7

  1. Install the scan tool.
  2. Place the headlamp switch in the OFF position.
  3. With a scan tool, observe the LCM Lights On Chime Input parameter in the body control module (BCM) data display inputs.

Does the scan tool indicate that the Lights On Chime Input parameter is ON?

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Go to Step 14

Go to Step 8

8

  1. Place the ignition switch in the OFF position.
  2. Toggle the headlamp switch ON and OFF.
  3. Place the headlamp switch in the PARK position.

Do the park lamps operate from the headlamp switch?

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Go to Step 9

Go to Park, License, and Tail Lamps Inoperative

9

  1. Turn headlamp switch to the OFF position.
  2. Disconnect the BCM.
  3. Using a test lamp connected to ground and probe the exterior lamps OFF input circuit of the BCM.

Does the test lamp illuminate?

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Go to Step 14

Go to Step 10

10

Test for an open or high resistance in the exterior lamps OFF circuit of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 18

Go to Step 13

11

Test for poor connection, open or short to ground in the daytime running lamps (DRL) ambient light sensor signal. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 18

Go to Step 12

12

Inspect for poor connections at the harness connector of 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?

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Go to Step 18

Go to Step 15

13

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

Did you find and correct the condition?

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Go to Step 18

Go to Step 16

14

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 18

Go to Step 17

15

Replace the ambient light sensor. Refer to Daytime Running Lamp (DRL) Ambient Light Sensor Replacement .

Did you complete the replacement?

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Go to Step 18

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16

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

Did you complete the replacement?

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Go to Step 18

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17

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 18

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18

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2