Diagnostics and testing of front fog lamps (Discovery 3)

Inspection and verification

1. Make sure the customer's complaint is valid.

2. Visually inspect for obvious electrical problems.

Mechanical factors	Electrical Factors
Condition and installation of front fog lights Lamps and installation Lamp holders and installation Adjusting screw Condition and installation of the fog lamp switch	Fuses Battery Electrical Junction Box (BJB) - fuse link 2E BJB - fuse link 11E Central electrical box (CJB) - fuse 28P CJB - fuse 38P Wiring harness Loose or corroded connector (ov) Fog lamp relay Fog lamp warning lamp Fog light switch Battery Electrical Junction Box (BJB) Central electrical box (CJB)

3. If an obvious cause of a problem you identified or described by a customer is found, resolve it before proceeding to the next steps (if possible).

4. Use an approved diagnostic system or scan tool (tester), to retrieve all DTCs before referring to the symptom table or DTC index (DTC).

Since DTCs are stored in more than one module, a complete vehicle data readout is recommended.

Clear all DTCs after troubleshooting.

Symptom table

Symptom	Possible reasons	Action
Fog lights not working	Lamp failure Fuse (And) burned out Electrical circuit malfunction Switch not working	Check the condition of the lamp. Check fuse (And) (see visual inspection). Check the fog lamp electrical circuits. Check switch operation. Refer to the electrical manual.
Adjusting the brightness of the fog lights	Incorrect lamp power Electrical circuit malfunction Switch failure	Check the condition and power of the lamp. Check the fog lamp electrical circuits. Check switch operation. Refer to the electrical manual.
Insufficient area of illumination provided by fog lamps	Fog lamp misalignment	Check and adjust fog lamp alignment.
The control lamp does not work	Fuse (And) burned out Switch not working Electrical circuit malfunction Instrument panel malfunction	Check fuse (And) (see visual inspection). Check switch operation. Check the test lamp electrical circuits. refer to the electrical manual. Check for DTCs (DTC), indicating a malfunction in the instrument panel.

DTC index

NOTE: Universal Scan Tools cannot read the listed codes or can only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7 digit code to identify the problem (the last 2 digits give additional information read by the diagnostic system approved by the manufacturer).

DTC	Description	Possible reasons	Action
B1A7864	Front fog lights	Lack of signal plausibility	Check instrument cluster module and circuits. Refer to the electrical manual.
B1D4013	Light switch connection circuit	Light switch connection circuit open circuit	Refer to the guided diagnostic program for this code on the approved diagnostic system. Refer to the electrical manuals and check the switch circuit. Replace/repair as needed.