Finding codes /wiring woes
 

First of all, the check engine light came on at 80,000 miles in my 1993 300 E. OK, I replaced the Oxygen Sensor unit and all was well. Now, at 100,000, it has come on again. Mpg is great, runs great...how do I read the code without spending big bucks?

Second, Over the past few months several things happened intermittantly, but always together. Most of these are on one fuse and the symptoms make me think something is going to ground somewhere. I would loose my central locking system, my stereo quit and read E2, the interior light serviced by the door jam switch stayed on, and the fasten steat belt light blinked. Usually these quit after a day or two, but now it's all the time. Any ideas?

On some cars the "check engine" comes on every so many miles whether there's a problem or not. Check around for that (owners manual or a repair manual) On my old Audis the oxygen sensor light comes on at every 30K miles. I know where the reset button is, so if the car is running ok, I just hit the reset button and ignore it.

I've reset the light...it comes back on after 30-40 miles.

Ok. Bad suggestion. Keep us posted if you find out what's up. Sounds strange.

where's the ground?
 

How do you get to the ground located behind the dash in a 1993 300E?

One cluster of ground wires is located behind the instrument cluster. Another cluster is located underneath the ashtray/ center console woodgrain area.
Examine the engine wiring harness carefully. The insulation is known to biodegrade exposing bare wire.
:)