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Rear 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

Headlamp Switch 12V Reference

1

1

1

--

Headlamp Switch Signal

1

1

2

--

1. Rear Fog Lamps Inoperative

2. Rear Fog Lamps Always ON

Circuit/System Description

The rear fog lamp switch signal circuit is grounded through a resistor momentarily by pressing the rear fog lamp switch. The body control module (BCM) energises the rear fog lamp supply voltage circuit which illuminates the rear fog lamp. With the rear fog lamp switch activated the BCM sends a message via serial data to the instrument cluster requesting the instrument cluster to illuminate the rear fog indicator.

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

  1. Ignition ON, perform the scan tool Rear Fog Lamps Switch parameter. The reading should change between Active/Inactive when changing between pressed and released rear fog lamp switch button.
  2. If the parameter does not cycle between the specified values, refer to Rear Fog Lamp Switch Malfunction.
  3. Ignition ON, perform the scan tool Rear Fog Lamps Relay test. Verify the rear fog lamps turn ON and OFF.
  4. If the rear fog lamps do not cycle between the commanded states, refer to Rear Fog Lamp Malfunction.
  5. Ignition ON, perform the instrument cluster All Indicators test ON and OFF test. The rear fog indicator should be ON/OFF.
  6. If the rear fog indicator do not cycle between the commanded states, refer to Rear Fog Indicator Malfunction.

Circuit/System Testing

Rear Fog Lamp Switch Malfunction

  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 2.0-2.4 kΩ between the signal circuit terminal 9 X1 and the 12 V reference voltage circuit terminal 4 X3 while pressing the rear 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.

Rear Fog Lamp Malfunction

  1. Ignition OFF, disconnect the harness connector at the E29R Fog Light - Rear.
  2. Test for less than 5 Ω between the ground circuit harness connector terminal 3 and ground.
  3. If greater than the specified value, test the appropriate ground circuit for an open/high resistance.
  4. Connect a test lamp between the control circuit harness connector terminal 2 and ground.
  5. Ignition ON, perform the Rear Fog Lamps Relay test. The test lamp should be ON/OFF when changing between the commanded states.
  6. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
    If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K9 Body Control Module.
  7. If all circuits test normal, test or replace the E29R Fog Light - Rear.

Rear Fog Indicator Malfunction

Ignition ON, command the instrument cluster All Indicators test ON and OFF with the scan tool. The rear fog indicator lamp should be ON/OFF when changing between the commanded states.

If the rear fog indicator stays always on or always off, replace the P16 Instrument Cluster.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Reversing and Rear Fog Light Replacement
    •  Headlamp Switch Replacement
    • Control Module References for BCM or instrument panel cluster replacement, setup and programming
   


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