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DTC B2740

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 B2740 00: Front Fog Lamp Switch Circuit Malfunction

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Front Fog Lamp Control

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B2740 00

Circuit/System Description

The front fog lamp relay is supplied with battery voltage at all times. The front fog lamp switch signal circuit is grounded through a resistor momentarily by pressing the front fog lamp switch. The body control module (BCM) energises the front fog lamp relay by applying ground to the front fog lamp relay control circuit. When the front fog lamp relay is energised, the relay switch contacts close and battery voltage is applied through the front fog lamp fuse to the front fog lamp supply voltage circuit which illuminates the front fog lamps.

Conditions for Running the DTC

    • The ignition is turned ON.
    • Front fog lamp switch activated.

Conditions for Setting the DTC

Front fog lamp switch stuck.

Action Taken When the DTC Sets

The front fog lamps are inoperative.

Conditions for Clearing the DTC

The condition for setting the DTC is not longer present.

Reference Information

Schematic Reference

Fog Lamps 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 Lamps Switch parameter. The reading should change between Active/Inactive when changing between pressed and released front fog lamp switch button.

Circuit/System Testing

  1. Ignition OFF, disconnect the X1 and X3 harness connectors at the K9 Body Control Module.
  2. Ignition ON, test for less than 0.3 V between the signal circuit terminal 9 X1 and ground.
  3. If greater than the specified value, test the circuits listed below for a short to voltage. If the circuit tests normal, replace the S30 Headlamp Switch.
    • Signal circuit terminal 9 X1
    • 12 V reference voltage circuit terminal 4 X3
  4. Ignition OFF, test for infinite resistance between the signal circuit terminal 9 X1 and ground.
  5. If less than infinite resistance, test the circuits listed below for a short to ground. If the circuit tests normal, replace the S30 Headlamp Switch.
    • Signal circuit terminal 9 X1
    • 12 V reference voltage circuit terminal 4 X3
  6. Test for 7.4-7.9 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3.
  7. If less than 7.4 kΩ, test the signal circuit and the 12 V reference circuit for a short circuit. If the circuit tests normal, replace the S30 Headlamp Switch.
    If greater than 7.9 kΩ, test the signal circuit and the 12 V reference circuit for an open/high resistance. If the circuit tests normal, replace the S30 Headlamp Switch.
  8. Test for 2.7-3.1 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3 while pressing the front fog lamp switch.
  9. If not the specified range, replace the S30 Headlamp Switch.
  10. If all circuits test normal, replace the K9 Body Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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


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