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Front Fog Lamps Malfunction



Front Fog Lamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

With both the ignition switch in the RUN position and the park lamps or low beam head lamps ON, the fog lights will illuminate when the driver presses the fog lamp switch. The FOG LP fuse in the underhood fuse block supplies battery positive voltage to the fog lamps. With the headlamp switch is in either the park or headlamp position and the fog lamp switch is pressed, the body control module (BCM) will energize the fog lamp relay control circuit. The current flow is from the fog lamp relay to both front fog lamps and to ground G105. The state of the fog lamps, either ON or OFF, will remain the same until the fog lamp switch is pressed again, or the ignition switch is cycled OFF and ON. Fog lamp operation will be cancelled whenever the park lamps are turned OFF or the high beam headlights have been selected.

Reference Information
Schematic Reference

Fog Lights Schematics (Fog Lights Diagram)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, command the front fog lamps ON and OFF with a scan tool. The front fog lamps should turn on and off.

• If the fog lamps do not turn on and off, refer to Fog Lamp Relay Circuit Test.

2. Ignition ON, observe the scan tool front fog lamp switch parameter while pressing the front fog lamp switch. The reading should change between inactive and active.

• If not the specified value, refer to Fog Lamp Switch Circuit Test.

Circuit/System Testing

Fog Lamp Relay Circuit Test
1. Ignition OFF, disconnect the front fog lamp relay.
2. Test for less than 5 ohms between the relay coil ground circuit terminal 86 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify a test lamp does not illuminate between the fog lamp control circuit terminal 30 and ground.

• If the test lamp illuminates, test the fog lamp control circuit for a short to voltage.

4. Verify a test lamp illuminates between the relay switch B+ circuit terminal 87 and ground.

• If the test lamp does not illuminate, replace the underhood fuse block.

5. Disconnect the harness connector at an affected fog lamp.
6. Ignition OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the fog lamp.
8. Ignition ON, connect a 15A fused jumper wire between the relay switch B+ circuit terminal 87 and the fog lamp control circuit terminal 30. Verify the front fog lamps are on.

• If the front fog lamps do not turn on, test the fog lamp control circuit for an open/high resistance. If the circuit tests normal, test or replace the affected fog lamp bulb.
• If the fuse in the jumper wire opens, test the fog lamp control circuit for a short to ground.

9. Connect a test lamp between the relay coil control circuit terminal 85 and ground.
10. Command the front fog lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• 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.

Fog Lamp Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition ON, verify the scan tool front fog lamp switch parameter is inactive.

• If not the specified value, test the signal circuit terminal 7 for a short to ground. If the circuit tests normal, replace the BCM.

3. Install a 3A fused jumper wire between the signal circuit terminal 7 and the low reference circuit terminal 3. Verify the scan tool front fog lamp switch parameter is active.

• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the headlamp switch.

Component Testing

Relay Test
1. Ignition OFF, disconnect the front fog lamp relay.
2. Test for 70-100 ohms between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 30 and 85
* 30 and 86
* 30 and 87
* 85 and 87

• If not the specified value, replace the relay.

4. Install a 10A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

• If greater than the specified range, replace the relay.

Fog Lamp Switch Test
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for infinite resistance between the signal terminal 7 and the low reference terminal 3.

• If not the specified value, replace the headlamp switch.

3. Test for less than 5 ohms between the signal terminal 7 and the low reference terminal 3 while pressing the front fog lamp switch.

• If greater than the specified range, replace the headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Front Fog Lamp Bulb Replacement (Canyon) (Service and Repair)
* Headlamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming

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