GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 XLR 🢒 Body Systems 🢒 Lighting 🢒 Front Fog Lamps Malfunction

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Front Fog Lamp Switch Signal

2

2

2

--

Front Fog Lamp Relay Control

B2530 02

B2530 05

B2530 05

--

Front Fog Lamp Control

1

1

1

--

Front Fog Lamp Relay Ground

--

1

1

--

Fog Lamp - LF Ground

--

1

1

--

Fog Lamp - RF Ground

--

1

1

--

Fog Lamp Switch Ground

--

2

2

--

1. Front Fog Lamps Malfunction

2. Front Fog Lamp Switch Malfunction

Circuit/System Description

The front fog lamp switch signal circuit is grounded momentarily by pressing the front fog lamp switch. The body control module (BCM) energizes the front fog lamp relay by applying battery voltage to the front fog lamp relay control circuit. When the front fog lamp relay is energized, battery voltage is applied via the FOG LAMP fuse to the front fog lamp supply voltage circuit which illuminates the front fog lamps. The BCM sends a serial data message to the instrument panel cluster (IPC) to enable the front fog lamp indicator.

Reference Information

Schematic Reference

Fog Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool Front Fog Lamp Switch parameter while pressing and releasing the front fog lamp switch. The reading should toggle between Active and Inactive.

⇒If the reading does not change between the commanded states, refer to Front Fog Lamp Switch Malfunction.

Circuit/System Testing

Front Fog Lamp Switch Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
  2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 3.
    3. ⇒If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the scan tool Front Fog Lamp Dwitch parameter is Inactive.
    4. ⇒If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the BCM.
  4. Install a 3A fused jumper wire between the signal circuit terminal 4 and the ground circuit terminal 3. Verify the scan tool Front Fog Lamp Switch parameter is Active.
    5. ⇒If not the specified value, test the signal circuit terminal 4 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the turn signal/multifunction switch.

Front Fog Lamps Malfunction

  1. Ignition OFF, disconnect the front fog lamp relay.
  2. Test for less than 5 ohms between the ground circuit terminal C3 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal C4 and ground.
    4. ⇒If the test lamp illuminates, test the control circuit for a short to voltage.
  4. Verify that a test lamp illuminates between the B+ circuit terminal A3 and ground.
    5. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal C4 for a short to ground. If the circuit tests normal, test or replace the front fog lamp relay.
  5. Disconnect the harness connector at the Inoperative front fog lamp.
  6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.
    7. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the inoperative front fog lamp.
  8. Connect a 15A fused jumper wire between the B+ circuit terminal A3 and the control circuit terminal C4. Verify the front fog lamps are activated.
    9. ⇒If the front fog lamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative front fog lamp.
  9. Connect a test lamp between the control circuit terminal A4 and ground.
  10. Command the front fog lamps ON and OFF with the front fog lamp switch. The test lamp should turn ON and OFF when changing between the commanded states.
    11. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the BCM.
  11. If all circuits test normal, test or replace the front fog lamp relay.

Front Fog Lamp Indicator Malfunction

Ignition ON, with a scan tool perform the display test for the IPC and observe the front fog lamp indicator.

⇒If the front fog lamp indicator illuminates during the test, replace the BCM.
⇒If the front fog lamp indicator does not illuminate during the test or remains illuminated at all times, replace the IPC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Fog Lamp Replacement
    •  Underhood Electrical Center or Junction Block Replacement
    •  Relay Replacement
    •  Turn Signal Multifunction Switch Replacement
    •  Control Module References for BCM or IPC replacement, setup, and programming