GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 LaCrosse 🢒 DTC 🢒 DTC B2525

Circuit Description

The fog lamp relay is energized by the fog lamp switch only when the body control module (BCM) has activated the fog lamp enable circuit that supplies the fog lamp switch. The BCM will only activate the fog lamp enable circuit if the following conditions exist:

    • The ignition switch must be in the RUN position.
    • The headlamp switch must be in the park or headlamp ON position.
    • The headlamp dimmer switch must be in the low beam position.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2525 Front Fog Lamp Enable Circuit

Conditions for Running the DTC

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

Conditions for Setting the DTC
    •  The fault code will set when the fog lamp enable circuit is active and a short to battery positive voltage, an open or a short to ground is present.
    • The condition above must be present for more than 0.3 seconds.
    • If the short to battery positive voltage is on the output side of the fog lamp switch, the fault will only set when the fog lamp switch is in the ON position.

Action Taken When the DTC Sets

The BCM stores DTC B2525 in memory.

Conditions for Clearing the DTC
    • A current DTC B2525 will clear if the short to battery positive voltage, a short to ground or an open in the fog lamp enable circuit is no longer detected by the BCM.
    • A history DTC B2525 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • The BCM receives a clear code command from the scan tool.

Diagnostic Aids
    • If the DTC B2525 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .
    • The following conditions may cause an intermittent malfunction to occur:
       - An intermittent short to battery positive voltage, a short to ground or an open in the fog lamp enable circuit.
       - The fog lamp relay coil is intermittently shorted to battery.
       - The BCM is intermittently shorted to battery positive voltage, shorted to ground or an open.

Step

Action

Yes

No

Schematic Reference: Fog Lights Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Place the headlamp switch in the HEAD position.
  4. Place the headlamp dimmer switch in the LOW beam position.
  5. With a scan tool, observe the Front Fog Lamp Relay parameter in the body control module (BCM) data list outputs.
  6. Turn the fog lamp switch ON and OFF.

Does the Fog Lamp Relay parameter change state?

Go to Diagnostic Aids

Go to Step 3

3

  1. Disconnect the FOG LP relay.
  2. Turn the fog lamp switch OFF.
  3. Using a test lamp connected to ground, probe the FOG LP relay control circuit at the underhood fuse block.

Does the test lamp illuminate?

Go to Step 4

Go to Step 6

4

  1. Disconnect the BCM connector C1.
  2. Using a test lamp connected to ground, probe the fog lamp relay control circuit at the underhood fuse block.

Does the test lamp illuminate?

Go to Step 5

Go to Step 14

5

Test the control circuit of the fog lamp relay for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 15

Go to Step 12

6
  1. Turn the ignition to the ON position.
  2. Place the headlamp switch to the HEAD position.
  3. Place the headlamp dimmer switch to the LOW beam position.
  4. Turn the fog lamp switch to the ON position.
  5. Using a test lamp connected to battery positive voltage, probe the fog lamp relay control circuit.

Does the test light illuminate?

Go to Step 9

Go to Step 7

7
  1. Turn the ignition to the OFF position.
  2. Place the headlamp switch to the OFF position.
  3. Place the fog lamp switch to the OFF position.
  4. Disconnect the BCM connector C1.
  5. Install a jumper between the fog lamp control circuit and ground.
  6. Using a test lamp connected to battery positive voltage, probe the fog lamp relay control circuit at the underhood fuse block.

Does the test lamp illuminate?

Go to Step 14

Go to Step 8

8

Test for a poor connection or an open in the fog lamp relay control circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 15

Go to Step 12

9
  1. Turn the ignition to the OFF position.
  2. Place the headlamp switch to the OFF position.
  3. Place the fog lamp switch to the OFF position.
  4. Disconnect the BCM connector C1.
  5. Using a test lamp connected to battery positive voltage, probe the fog lamp relay control circuit at the underhood fuse block.

Does the test lamp illuminate?

Go to Step 10

Go to Step 11

10

Test for a short to ground in the fog lamp relay control circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 15

Go to Step 12

11
  1. Reconnect the BCM.
  2. Turn the ignition to the ON position.
  3. Place the headlamp switch to the HEAD position.
  4. Place the headlamp dimmer switch to the LOW beam position.
  5. Turn the fog lamp switch to the ON position.
  6. Using a test lamp connected to battery positive voltage, probe the fog lamp relay control circuit at the underhood fuse block.

Does the test lamp illuminate?

Go to Step 13

Go to Step 14

12

Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement .

Did you complete the replacement?

Go to Step 15

--

13

Replace the fog lamp relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 15

--

14

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 15

--

15
  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