Mercedes C-Class W205 Electrical Gremlins — CAN Bus & Dashcam Interference

CUSTOMER COMPLAINT

The owner described a car behaving erratically: random dashboard warnings appearing and clearing, lights flickering, and the keyless entry working one moment and not the next.

SYMPTOMS

Intermittent dashboard warning messages, flickering interior and exterior lights, and unreliable keyless entry and central locking. No single fault was consistent.

DIAGNOSTIC PROCESS

A full diagnostic scan returned a mix of communication and voltage-related codes with no obvious single culprit. Because the symptoms pointed to electrical interference, we used an oscilloscope to monitor the CAN bus and the vehicle's power rails live, looking for noise or voltage drop while the faults occurred.

FAULT FOUND

An aftermarket dashcam, poorly installed by a previous owner, had been tapped into a circuit that shared wiring with the CAN bus and was injecting electrical noise onto the network — corrupting messages and producing the random faults.

REPAIR / SOLUTION

The dashcam's incorrect wiring was removed and the feed restored to a proper, isolated supply. The affected wiring was inspected and protected, and the CAN bus was re-checked on the oscilloscope to confirm a clean signal with no interference. Fault codes were cleared.

RESULT

The random warnings, flickering and keyless issues all stopped once the interference was removed. The CAN bus verified clean, and the customer kept the dashcam — just rewired properly.