Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Rear fog lamp
The rear fog lamp are in the tail lamps. The fog lamps are operated via a button in the light switch module (LSM). An LED in the button lights when the fog lamps are activated. The rear fog lamp can only be activated when low beam is on (market dependent). The light switch transmits information to the central electronic module (CEM) using serial communication when the button for the rear fog lamp is pressed. The central electronic module (CEM) transmits the data via the Controller area network (CAN) to the rear electronic module (REM). The power supply for the lamps is via a directly connected relay in the rear electronic module (REM).
When reactivating key position II, the function is set to non-activated mode.
To detect faults in the rear fog lamps, the rear electronic module (REM) reads the power consumption of the circuit. If the power consumption falls below a certain limit, a fault is indicated and a text message is displayed in the driver information module.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.