GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Regal (China) 🢒 DTC 🢒 DTC B3590

Circuit Description

With the front fog lamps on or headlamps on the Body Control Module (BCM) receives an momentary ground input from the rear fog lamps switch when the rear fog lamp switch is pressed. Upon receiving the input, the BCM pulls low the rear fog lamp relay control circuit which energizes the rear fog lamp relay. Pressing the rear fog lamp switch again will de-energize the rear fog lamp relay

Conditions for Running the DTC

The fault is present for 5 minutes while the ignition is ON and the BCM is awake.

Conditions for Setting the DTC
    • The rear fog lamp switch input of the BCM is shorted to ground.
    • The rear fog lamp switch is closed at all times.
    • The conditions above must be present for more than 5 minutes.

Action Taken When the DTC Sets

The BCM stores DTC B3590 in memory.

Conditions for Clearing the DTC
    • A current DTC B3590 will clear if the short to ground in the rear fog lamp switch input circuit is no longer detected by the BCM.
    • A history DTC B3590 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present nor any other malfunction in the BCM is detected.
    • The BCM receives a clear code command from the scan tool.

Diagnostic Aids
    • If the DTC B3590 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 ground in the rear fog lamps switch input circuit
       - The rear fog lamp switch is always closed
       - The BCM is intermittently shorted to ground

Test Description

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

  1. This step determines if the rear fog lamp input is in its normal state.

    2.

  2. This step determines if the rear fog lamp switch is operating properly.

    3.

  3. This test determines if the rear fog lamp switch is always closed.

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, observe the rear fog lamp switch input parameter in the Body Control Module data list.

Does the scan tool display OFF?

Go to Step 3

Go to Step 4

3

  1. Press the rear fog lamp switch.
  2. With the scan tool, observe the rear fog lamp switch input parameter.

Does the rear fog lamp switch input parameter change state?

Go to Diagnostic Aids

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the rear fog lamp switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the rear fog lamp switch input parameter.

Does the scan tool display OFF?

Go to Step 7

Go to Step 5

5

Test the rear fog lamp switch input circuit of the BCM 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 8

Go to Step 6

6

Important: Perform the set up procedure for the BCM.

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

Did you complete the replacement?

Go to Step 8

--

7

Replace the rear fog lamp switch. Refer to Rear Fog Lamp Switch Replacement .

Did you complete the replacement?

Go to Step 8

--

8
  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