GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Classic - 4WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Park, License, and Tail Lamps Always On

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Verify that the park, license and tail lamps are always ON.

Do the park, license and tail lamps operate normally?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Remove the park lamp relay.

Do the park lamps turn OFF?

Go to Step 4

Go to Step 9

4
  1. Ensure that the headlamp switch is in the AUTO position and there is sufficient light to the ambient light sensor.
  2. Test for a ground signal at the park lamp relay control circuit terminal in the underhood fuse block. Refer to Circuit Testing .

Was a ground signal present?

Go to Step 5

Go to Step 10

5

Use the scan tool to check the body control module (BCM) park lamp switch input data.

Does the scan tool indicate a park lamps OFF request signal?

Go to Step 8

Go to Step 6

6

Test for a short to ground in the park lamp switch signal circuit. Refer to Circuit Testing Wiring Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 7

7

Inspect for poor connections at the harness connector of the headlamp switch. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 11

8

Inspect for poor connections at the harness connector of the BCM. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 12

9

Repair the short to voltage in one of the following circuits:

    • Front park lamp supply voltage
    • Trailer park lamps supply voltage
    • Right rear park lamps supply voltage
    • Left rear park lamps supply voltage
    • Interior park lamps supply voltage

Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 13

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10

Replace the park lamp relay. Refer to Relay Replacement .

Did you complete the repair?

Go to Step 13

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11

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Did you complete the repair?

Go to Step 13

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12

Replace the BCM. Refer to Control Module References .

Did you complete the replacement?

Go to Step 13

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13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3