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DTC B3588

DTC B3588

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 B3588 00

Rear Fog Lamp Switch Circuit Malfunction

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Headlamp Switch Reference Voltage B257B 03 B257B 03 - B3588 00
Headlamp Switch Signal B257B 03 B257B 03 B257B 07 -


Circuit/System Description

The body control module (BCM) supplies a reference voltage to the backlight dimmer switch, which is part of the headlamp switch. When the backlight dimmer switch is placed in a desired brightness position, reference voltage is applied through the backlight dimmer switch resistor ladder to the BCM. The BCM interprets this voltage signal and will command the interior lights to the desired brightness, command the front fog lamps or the rear fog lamps depending upon the switch setting selected.

Conditions for Running the DTC


• The ignition is turned ON.

• Low beam or front fog lamps illuminated.

• Rear fog lamp switch activated.


Conditions for Setting the DTC

Rear fog lamp switch stuck.

Action Taken When the DTC Sets


• All cluster/backlighting defaults full bright

• Steering wheel cluster/backlighting dimming controls inoperative

• Front fog lamps are inoperative

• Rear fog lamps are inoperative


Conditions for Clearing the DTC


• The DTC will be current for as long as the fault is present.

• When the fault is no longer present, the DTC will be a history DTC.

• A history DTC will clear after 40 ignition cycles.


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 Rear Fog Lamps Switch parameter. The parameter should change between Active and Inactive each time the rear fog lamp switch is pressed.

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.

2. Ignition OFF, test for 0.4k Ω to 1 Ω between the signal circuit terminal 12 and ground.

3. If greater than the specified value, test the low reference circuit for an short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

4. If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 BCM.

5. Test for greater than 10 V between the 12 V reference circuit terminal 1 and ground.

6. If less than the specified range, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

7. If all circuits test normal, replace the K9 BCM.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Headlamp Switch Replacement

• Control Module References for BCM replacement, programming and setup