Fog/Driving Lamp: Description and Operation

FOG LAMPS

Principles of Operation

NOTE:The smart junction box (SJB) is also known as the generic electronic module (GEM).
The SJB monitors the headlight switch position by sending a voltage reference signal to the headlight switch. When the fog lamp switch is engaged, the voltage reference signal is routed to ground.The fog lamps can be turned on when the following conditions are met:

- The ignition switch is in the RUN or START position.
- The low beam headlamps or the parking lamps are on.
- The high beams are off.When the SJB receives an input from the headlight switch indicating a request for the fog lamps, the SJB provides ground to the fog lamp relay (integrated into the SJB). When the fog lamp relay is energized, voltage is routed to the fog lamps.

Inspection and Verification

1. Verify the customer concern.

2. Visually inspect for obvious signs of electrical damage.
Visual Inspection Chart





3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.

NOTE:Make sure the headlight switch is in the OFF position.
NOTE:Make sure the multifunction switch is in the LOW BEAM position.
4. If the cause is not visually evident, connect the scan tool to the data link connector (DLC).

NOTE:Make sure to use the latest scan tool software release.
5. If the scan tool does not communicate with the VCM:

- Check the VCM connection to the vehicle.
- Check the scan tool connection to the VCM.
- See , to diagnose no power to the scan tool.

NOTE:The vehicle communication module (VCM) LED prove-out confirms power and ground from the DLC are provided to the VCM.
6. If the scan tool does not communicate with the vehicle:

- Verify the ignition key is in the ON position.
- Verify the scan tool operation with a known good vehicle.
- See Pinpoint Test 1: The PCM Does Not Respond To The Scan Tool, to diagnose no response from the PCM.

7. Carry out the network test.

- If the scan tool responds with no communication for one or more modules, see Description and Operation.
- If the network test passes, retrieve and record the continuous memory DTCs.

8. Clear the continuous DTCs and carry out the self-test diagnostics for the SJB.

9. If the DTCs retrieved are related to the concern, see - Lighting Systems - Diagnostic Trouble Code (DTC) Chart - Lighting Systems. For all other DTCs, see - Control Systems - Diagnostic Trouble Code (DTC) Chart - B, C And U Codes.

10. If no DTCs related to the concern are retrieved, see - Symptom Related Diagnostic Procedures.