Taking into consideration your circumstance, I might disconnect the negative connection to the battery for a short time which in turn will clear fault codes. While the battery is disconnected, I would use the time to visually check all the connection on the upper wiring harness. (Just remove the air filter housing and the front cover – you don’t need to remove any of the engine side covers to review the upper wiring connections.)

Reconnect the negative battery terminal in the trunk (battery). Take a long screwdriver and place it on you ear as you listen to each fuel injector. Kind of like a stethoscope. You should hear a clicking nose coming from each injector. If no clicking nose, check the wire connection to the injector.

Drive the car for a few days as the Control Unit adapts to the new values. If new codes are generated, the shop will know the code were generated after the wiring harness replacement.

I the problem persists, have the codes check at a MB equipped shop. It will have to be a MB shop since the plug for the code reader is an OBDI Mercedes specific connector.

There are numerous other technical steps you could take to look for problems, but this might be good 1st step.

You didn't make mention the car's performance. I assume without the gas milage problem, it's okay?

Later you might want to review the O2 sensor, rotor caps, rotors, plugs, air filter, (tune up items)

Good luck!

__________________
Russell McMahon
Tulsa, OK
2001 CLK 320
1992 400se
1993 400e
2000 320ML