GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Monte Carlo 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC B2742 Fog Lamp Switch Circuit Low

Circuit Description

The fog lamp switch provides a direct ground input into the Body Control Module (BCM) for the fog lamp switch state input when the switch is pressed. This input is used by the BCM to control the fog lamps.

Conditions for Setting the DTC

The BCM detects a short to ground in the fog lamp switch signal circuit for longer than 60 seconds.

Action Taken When the DTC Sets
    • The BCM stores DTC B2742 in memory.
    • The input and all input operations are disabled until fault is no longer detected.

Conditions for Clearing the DTC
    • A current DTC B2742 will clear if the BCM no longer detects a short to ground for longer than 60 seconds.
    • A history DTC B2742 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids
    • If the DTC B2742 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 ground in the fog lamp switch input circuit.
       - The fog lamp switch is intermittently grounded internally
       - The BCM is intermittently shorted to ground internally

Step

Action

Yes

No

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to A Diagnostic System Check - Lighting Systems in Lighting Systems.

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the fog lamp switch State input parameter in the Body Control Module (BCM) input data list.

Does the scan tool display Inactive?

Go to Step 3

Go to Step 4

3

Depress the fog lamp switch a couple of times while observing the input parameter on the scan tool.

Does the fog lamp switch state input parameter change state when it is depressed?

Go to Diagnostic Aids

Go to Step 4

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

Does the scan tool display Inactive.

Go to Step 7

Go to Step 5

5

Test the fog lamp switch input/signal 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 10

Go to Step 6

6

Inspect for poor connections at the harness connector of the Body Control Module. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 8

7

Inspect for poor connections at the harness connector of the fog lamp switch. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 9

8

Important: Perform the set up procedure for the Body Control Module.

Replace the Body Control Module. Body Control Module Replacement in Body Control Systems.

Did you complete the replacement?

Go to Step 10

--

9

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

Did you complete the replacement?

Go to Step 10

--

10
  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