GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Aztek - FWD 🢒 Body 🢒 Lighting Systems 🢒 DTC B2742

Circuit Description

The body control module (BCM) controls the fog lamps by grounding the coil side of the fog lamp relay when the fog lamp switch is pressed momentarily .

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2742 Front Fog Lamp Switch Circuit Low

Conditions for Running the DTC

Voltage supplied to the module is in the normal operating range, approximately 10-16 volts.

Conditions for Setting the DTC
    • The BCM detects a short to ground in the signal circuit of the fog lamp switch when the fog lamps are ON.
    • The condition must be present for at least 60 seconds.

Action Taken When the DTC Sets
    • The BCM stores B2742 in memory.
    • The fog lamps will not operate.

Conditions for Clearing the MIL/DTC
    • A current DTC B2742 clears when the BCM no longer detects a short to ground in the signal circuit of the fog lamp switch.
    • A history DTC B2742 clears after 100 consecutive ignition cycles.
    • The BCM receives the Clear Code command from the scan tool.

Diagnostic Aids
    • If the DTC B2742 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .
    • An intermittent short to ground in the following locations may cause an intermittent malfunction to occur:
       - The signal circuit of the fog lamp switch
       - The fog lamp switch
       - The BCM

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. With a scan tool, observe the Front Fog Lamps parameter in the body control module (BCM) data list.

Does the scan tool display OFF?

Go to Step 3

Go to Step 4

3

  1. Activate the fog lamps.
  2. With the scan tool, observe the Front Fog Lamps parameter.

Does the Front Fog Lamps parameter change state?

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 Front Fog Lamps parameter.

Does the scan tool display OFF?

Go to Step 7

Go to Step 5

5

Test the signal circuit of the fog lamp switch for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 6

6

Inspect for a poor connection at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 8

7

Inspect for a poor connection at the harness connector of the fog lamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 9

8

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

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