My E350 has developed a problem that is driving us crazy. It is still under warranty so I am passing this of the dealer, but they are not having much luck either. Twice now, my wife has gone to start the car when the electronics go nuts. And by nuts, I mean that virtually every warning about systems will come up (SRS, ABS, …), lights on only one side of car work. If we can get it to start, transmission won’t shift, the engine seems rough and the radiator fan gets faster and faster till you turn it off worried about it spinning out of the hood.

The first time this happened, we had a tow truck come and take it to the dealer. When I picked it back up on they indicated the all diagnostics passed except the battery failed under a load test so they replaced it. I also learned at this point that it started right up for them on Friday.

The second time his happened, my wife left it in the garage. The engine did seem to be running rough the night before on the way home from the movies the night before. When I got home about 8 hours after my wife had this issue, I tried it and sure enough it went hay wire for me as well and this time I videoed it. It was later Friday at that point, so I figured I would deal with it Monday. I tried it again about midnight and it started up fine showing now issues except for an engine light. I pulled the engine code which was a P0500 Vehicle Sender Malfunction (I found two of them). They next day, I drove the car to the dealer and left it for them to deal with it (they were closed when I dropped it off).

The dealer of course didn’t have any trouble either and their diagnostics were clean. I did make them watch the video which I have on YouTube so they didn’t just blow me off. They performed SDS short test and found 30G codes (don't know that that means), no communication with tail lamps, ESM, SCM, A/C. They performed independent tests on SCM, ESM, tail lamps and all communications tested ok. The replaced the PRE-FUSE BOX and the erased all codes.

The questions I have for the members of this forum are as follows:
Was replacing the PRE-FUSE box a legitimate way to address the issue?
(Replacing the battery was obviously not)

Did they do that because it was a cheaper fix that is likely the problem and are hopping it goes away?
(We are less than a year and 10k miles from the end of the warranty)

YouTube video. If the link below doesn’t work search, “ETW”, “E350”, “Failure” and it should come up

 

What they did is commonly referred to as "Easter Egging" but with all due respect they did try something. Maybe they've seen this work as a fix in a similar situation before. You are fortunate to have made the video for proof. Don't let go of this problem and keep all work records as long as you own the car.

 

Intermittent malfunction “may” be: as simple as speed sensor and/or associated wiring (located at each wheel), or worst case engine control module (ECM) - maybe a combination of all. Possibility to consider, moisture. Speak with service manager and shop foreman to open case with MB to assist/monitor/document repair given remaining warranty period.

 

I see no problem with them replacing the battery since they could not duplicate the problem. I've seen a 'similar' problem on a XK where I had the key on/engine off for an extended period of time, which in turn ran the batt down quite a bit, and when I tried to start the car alllll sorts of messages/warnings came on and the headlights/turn signals did alllll sorts of peculiar things. Corrected once the battery was charged up.

This type of problem happens often on aircraft, and when they cannot be duplicated by the ground crew, you replace the 'most likely" bad actor and fly again. Includes massaging the wiring prior to changing the most likely bad actor. Somehow I don't think in the automotive world they do a lot of harness massaging while trying to duplicate the problem.

 

My 2001 Audi A6 2.7T spent 4 months total at the dealer with gremlins. Turned out to be an intermittent break in the engine wiring harness.