GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon XL - 4WD 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC B2643

Circuit Description

The SEO 1 15 A fuse in the engine wiring harness junction block supplies battery positive voltage to both the ground illumination relay switch contacts and the ground illumination relay battery positive voltage circuit. When the driver or passenger door is opened the body control module (BCM) energizes the ground illumination relay. Current flow is from the ground illumination relay to both outside rear view mirror ground illumination lamps. The ground illumination lamps are grounded through the courtesy lamps relay at G200 and G203.

Conditions for Running the DTC
    • The system voltage must be between 9.0- 16.0 volts.
    • The ignition switch in the OFF position.
    • Unlock doors from the remote control door lock key fob or open any door.
    • The above conditions must be met for more than 0.5 seconds.

Conditions for Setting the DTC
    • The ground illumination lamps ON.
    • The ground illumination relay control circuit is shorted to battery voltage.
    • The above conditions must be met for 0.5 seconds.

Action Taken When the DTC Sets

The ground illumination lamps will not function.

Conditions for Clearing the DTC
    • This DTC will clear after a fault free ground illumination lamp operation.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    • A clear codes message is sent by the scan tool.

Diagnostic Aids

Important: Use the appropriate probe from the J 35616 connector test adapter kit for any probing of the electrical components in this table, in order to avoid damage to the terminals.

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Listen for an audible click when the ground illumination relay operates. Command both the ON and OFF states. Repeat the commands as necessary.

    2.

  2. Tests for voltage at the battery positive voltage side of the puddle lamp relay. The SEO1 fuse supplies power to the battery positive voltage side of the ground illumination relay.

    3.

  3. Verifies that the body control module is providing ground to the ground illumination relay.

    4.

  4. Tests if ground is constantly being applied to the ground illumination relay.

    5.

  5. After replacement of the BCM you must calibrate the new module for proper operation.

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the ground illumination relay ON and OFF.

Does the ground illumination relay turn ON and OFF with each command?

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the ground illumination relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the ground illumination relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

4

  1. Connect a test lamp between the ground illumination relay control circuit of the ground illumination relay and the battery positive voltage circuit of the ground illumination relay .
  2. With a scan tool, command the ground illumination relay ON and OFF .

Does the test lamp turn ON and OFF with each command?

Go to Step 8

Go to Step 5

5

Does the test lamp remain illuminated with each command?

Go to Step 7

Go to Step 6

6

Test the ground illumination relay control circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

7

Test the ground illumination relay control circuit 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 13

Go to Step 9

8

Inspect for poor connections at the ground illumination 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 13

Go to Step 11

9

Inspect for poor connections at the harness connector of the body control module. 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 13

Go to Step 12

10

Repair the battery positive voltage circuit of the ground illumination relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the ground illumination relay.

Did you complete the replacement?

Go to Step 13

--

12

Important: Perform the setup procedure for the body control module.

Replace the body control module. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 13

--

13
  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK