GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The fog lamp switch is a momentary switch and receives voltage on from the IGN 1 fuse in the instrument panel (I/P) fuse block. The body control module (BCM) monitors the switch on the front fog lamp switch signal circuit. When the switch is pressed voltage is supplied on the front fog lamp signal circuit only while the switch is held down.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2743 Fog Lamp Switch Circuit High

Conditions for Running the DTC

    • The ignition switch is in the RUN position.
    • The headlamp switch is in the headlamps ON or park lamps ON position.
    • The fog lamps are commanded ON.

Conditions for Setting the DTC

Any of the following conditions will set this DTC:

    • The front fog lamp signal circuit is shorted to voltage for 30 seconds.
    • The fog lamp switch sticks closed.

Action Taken When the DTC Sets

DTC B2743 is stored in the BCM memory.

Conditions for Clearing the DTC

    • The BCM receives the clear code command from the scan tool.
    • A current DTC will clear when the conditions for setting the DTC are no longer present.
    • A history DTC will clear after 100 malfunction-free ignition cycles.

Diagnostic Aids

If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .

Step

Action

Yes

No

Schematic Reference: Fog Lights Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the ignition, with the engine OFF.
  2. Place the fog lamp switch in the OFF position.
  3. Place the headlamp switch in the OFF position.

Do the fog lamps remain illuminated?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

Disconnect the fog lamp relay.

Did the fog lamps turn OFF?

Go to Step 4

Go to Step 6

4

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

Did you find and correct the condition?

Go to Step 8

Go to Step 5

5

Inspect for poor connections at the fog lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Repair a short to voltage in the front fog lamp supply voltage circuit. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 8

--

7

Replace the fog lamp relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 8

--

8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3