My 2007 Mercedes C280 4Matic is experiencing a complete electrical shutdown while driving, and I’m desperately seeking help. I’ve consulted numerous garages and auto electricians, but none have been able to definitively diagnose the issue, leading to costly and ineffective guesswork repairs.
The problem manifests unexpectedly regardless of speed. While driving normally, the RPM suddenly drops to zero, then may fluctuate briefly around 9 RPM before the engine shuts off completely. If I notice the initial RPM drop and apply pressure to the accelerator, the engine will continue running as long as I maintain pressure on the gas pedal. However, upon releasing the accelerator, the engine immediately shuts down.
To address this 2007 Mercedes C280 4Matic electrical shutdown, I have already attempted several repairs, including:
- Replacing the idle control valve (twice, currently a new one is installed).
- Changing the Bosch mass air flow sensor (initially with a used sensor which caused over-fueling, then reverted to the original MAF).
- Replacing the electric wires connecting the engine to the battery, along with the fuel pump relay and overload relay.
- Changing the ignition control unit.
Interestingly, disconnecting the wire to the idle control valve seemed to prevent the electrical shutdown issue, but introduced difficulty starting the car, particularly in the morning.
Subsequently, I disconnected another wire, circled in red in the image below. Since disconnecting this second wire, the car no longer shuts down while driving. However, I am unsure of the function of this wire and would greatly appreciate any insight.
The mechanics I’ve consulted believe the problem is electrical, while the electricians suggest it’s mechanical – leaving me in a frustrating diagnostic loop. If anyone has experienced a similar 2007 Mercedes C280 4Matic complete electrical shutdown or can identify the function of the disconnected wire in the image, your expertise would be invaluable.
