My 2007 Mercedes C280 4Matic has been experiencing a frustrating issue: it randomly shuts down while driving. I’ve consulted numerous mechanics and electrical specialists, but none have been able to pinpoint the exact cause, leading to costly and ineffective guesses. This problem is becoming increasingly disruptive and I’m hoping someone with experience with Mercedes electrical systems can offer some guidance.
The shutdown occurs without warning. While driving at any speed, the RPM gauge suddenly drops to zero, then may briefly fluctuate around 9 RPM before the engine completely cuts out. If I notice the RPM dipping and immediately accelerate, the car will continue running as long as I keep pressure on the gas pedal. However, as soon as I release the accelerator, the engine shuts down again.
To try and resolve this 2007 Mercedes C280 4matic complete electrical shutdown after driving issue, I’ve already replaced several components based on garage recommendations. These include a new idle control valve (and even tested a second one), a used Bosch mass air flow sensor (which caused separate fueling problems, so I reverted to the original MAF sensor, even though shutdowns occurred with both), electric wires connecting the engine to the battery, the fuel pump relay, the overload relay, and even the ignition control unit. Despite these replacements, the problem persists.
Interestingly, I discovered a temporary workaround. Disconnecting the wire connected to the idle control valve prevents the shutdowns from happening. However, this creates a new problem: very difficult cold starts in the morning.
Further experimentation led me to disconnect another wire, circled in red in the image below. Since disconnecting this second wire, the car no longer shuts down while driving, and the cold start issue seems to be resolved. However, I am uncertain what this wire controls and worry about potential long-term effects of leaving it disconnected. Any insight into the function of this wire would be greatly appreciated.
Adding to the confusion, electrical technicians suggest the issue is mechanical, while mechanics believe it’s electrical. This back-and-forth has been unhelpful and costly. If anyone has encountered a similar complete electrical shutdown after driving issue with a 2007 Mercedes C280 4Matic or has expertise in Mercedes electrical systems, your advice would be invaluable in diagnosing and resolving this perplexing problem.
