Originally Posted by gerryvz

This is absolutely incorrect. Wiring harnesses WERE an issue on 1992 model year V-8 cars (500E and 400E).

The 400E/E420 used Bosch LH injection, NOT HFM (which was used on the 6-cylinder M104 cars starting in model year 1993; 1992 M103 300Es used Bosch KE-Jet).

ETAs are a fairly common failure (due in large part to the same issues with their internal wiring as the upper wiring harnesses have) but again you need to do some things before you start throwing parts at the problem.

Don't bother changing out fuel filters until you do the following:

a) replace the wiring harness, particularly if you don't know for sure that it has been previously changed. That is a baseline that you MUST do.

b) Pull the codes using the home-made code reader as mentioned previously.

You may gain some benefit from the forum at ********* Galactic HQ as it shares the same engine, and there are a few 400E owners/experts on that forum (as well as a fairly new sub-forum that is specific to the 400E/E420).

Don't throw money and parts at the problem until you replace the upper harness, and pull the codes (in that order). The codes will point toward the real issues. The reason I say to replace the harness first is that it is tied into the proper operation of the engine; and a faulty harness has also been known to fry one or more of the car's computers. Not saying that it will happen, but it certainly has.

Cheers,
Gerry

Originally Posted by Will_w202

Really! Learn something new every day. I've seen the opposite posted here several times. Why have I been told otherwise? And why does my 92SL not have the harness issues? What does the harness have to do with LH? Did they use a biodegradable harness on one assembly line and not on another? Interesting. I've always heard it was the 93-95 cars that had the issue.