GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) controls the park lamp relay. The BCM grounds the park lamp relay coil control circuit which energizes the park lamp relay.

Conditions for Running the DTC

The BCM must be commanding the park lamp relay to energize.

Conditions for Setting the DTC

    • The BCM detects a short to battery in the park lamp relay coil control circuit when the BCM is trying to energize the park lamp relay.
    • The condition above must be present for more than 0.3 seconds.

Action Taken When the DTC Sets

The BCM stores DTC B2588 in memory.

Conditions for Clearing the DTC

    • The BCM no longer detects a short to battery in the park lamp relay coil control circuit when the park lamp relay is commanded to energize.
    • A history DTC B2588 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

    • If the DTC B2588 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • The following conditions may cause an intermittent malfunction to occur:
       - An intermittent short to battery in the park lamp relay coil control circuit.
       - The park lamp relay coil is shorted to battery internally.
       - The BCM is shorted to battery internally.

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 park lamp relay ON and OFF.

Does the park lamp 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 park lamp relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a test lamp connected to ground, probe the park lamp relay coil side voltage supply circuit.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

4

  1. Connect a test lamp between the park lamp relay coil side voltage supply and the park lamp relay control circuit.
  2. With a scan tool, command the park lamp 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 park lamp relay control circuit for a short to voltage or an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

7

Test the park lamp relay control circuit for a short to ground. Refer to Circuit Testing and to 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 park lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and to 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 to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

10

Replace the RH IP fuse block.

Did you complete the repair?

Go to Step 13

--

11

Replace the park lamp relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 13

--

12

Important: Perform the set up procedure for the body control module (BCM). Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System.

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

Did you complete the replacement?

Go to Step 13

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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