GM Service Manual Online
For 1990-2009 cars only

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.

DTC Descriptor

DTC B2527 00: Front Fog Lamps Circuit Low

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Front Fog Lamp Relay B+

B2530 00

B2530 00

--

--

Front Fog Lamp Control

1

1

1

--

Front Fog Lamp Switch Signal

B2527 00

2

2

--

Front Fog Lamp Relay and Indicator Control

B2530 00

B2530 00

B2530 00

--

Front Fog Lamp Ground

--

1

--

--

Headlamp Switch Ground

--

4

--

--

1. Fog Lamp Malfunction

2. Fog Lamp Switch Malfunction

Circuit/System Description

The front fog lamp relay coil is supplied with battery voltage when the ignition is in the RUN or CRANK position. The front fog lamp relay switch is supplied with battery voltage at all times. 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 ground to the front fog lamp relay control circuit. When the front fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the FRONT FOG fuse to the front fog lamp control circuit which illuminates the front fog lamps.

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The front fog lamp switch signal circuit is shorted to ground for 15 minutes.

Action Taken When the DTC Sets

The front fog lamps will be inoperative.

Conditions for Clearing the DTC

    • This DTC will clear on current status after the condition for setting the fault is corrected.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.

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 Testing

  1. Ignition OFF, disconnect the harness connector X4 at the turn signal/multifunction switch.
  2. Ignition ON, verify the scan tool front fog lamp switch parameter is OFF.
  3. If not the specified value test the front fog lamp switch signal circuit terminal E for a short to ground. If the circuit tests normal, replace the BCM.
  4. If all circuits test normal, test or replace the headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Headlamp Switch Replacement
    •  Control Module References for BCM replacement, programming, and setup