1994 E320 Engine Electrical Chain of Events
 

My E320 Wagon with 135,000 miles went into limp home mode a couple of months ago and the (very good) shop I go to (European Auto Solutions in Waltham) diagnosed the codes and replaced the ETA. Six weeks later the same sort of problem shows up and EAS replaced the brake light switch but warned me that the HFM may also be suspect. Sure enough, now it goes into limp home mode more often, resets after shutting off the car and restarting, and I am probably looking at another $1000+ repair to replace the HFM. Is it just bad luck or are these stupid things related somehow? My wife is ready to trade in the car for something more reliable. Already replaced the wiring harness a couple of years ago.

Get the codes and post them


http://www.peachparts.com/shopforum/showthread.php?t=107630

And you're still getting ASR warning light?

Yes the ASR light comes on as well
 

It clears when I restart the car.

Check MENU#24 (bottom of page) and look at the Neutral Safety Switch . . . if it's bad, you'll get the same symptoms. Replaced mine ($65) and it's good to go!

Much cheaper than a ECU.

Finally got time to read codes
 

I only have a single Code 6 on the OBD. The first time I (when the ETA was diagnosed as faulty) I had multiple 6 and 26 codes. Ed Owen at EAS thinks it possible that bad ETA wiring can also cause a problem (two months later???) with the ECU. The bad brake light switch could just be a coincidence since that is a common problem. He has found a used ECU that matches mine and the total installed cost is reasonable (much less than $1000+ for a new one from Mercedes or remanufactured from Beckman) and since it carries a one year warranty I will do that.

I just think it very odd that THREE things electrical could go south within two months but I am no expert.

As I posted, go get the codes at the HFM and EA modules .
The DM codes you are giving mean nothing except the stored codes in the other modules are effecting the Emmisions DM.[N/59 module]
See the earlier link I posted for you and go get the codes at #8 [HFM/SFI module] and #14 [ EA/CC module ] and post them. That is where the real codes are.
The push button DM is only emmissions related codes and CE lamp activation.

http://members.aol.com/ajdalton7/ledtool.jpg

Code "6" is usually associated w/ "going-bad-ETA" however it could be other parts as well such has the Brake Switch (B/S) and/or the neutral safety switch (NSW).

Not sure what that means other than the 'crumbling' wires in the ETA could have caused some damage to the ECU. If that were true, replacing the ETA would NOT have fixed the problem, even temporarily. So that's why I don't think it's the ECU.

It more than a coincidence since the B/S ***AND*** the NSW are part of the ETA 'circuit' and if you have read the threads here, you've seen that many times replaceing one or both, has fixed the "ETA-problem".

It's your money but you'd be VERY REMISS for not investigating the NSW first before replacing the ECU!

You should dump the codes in the other modules as I show in MENU#24. You need to see what's happening there before committing to a new ECU.

Chip, please follow this advice. You paid a lot of $$ for parts and service you probably didn't need. (And Neutral safety switches only cost about $20.00.)

I have a dying NSW that fails in Park, but starts fine in Neutral on the first start of the day -- if the previous night's temperature dropped below 50 degrees. And if the temperature fell below about 40 degrees, ASR/limp-home mode is often triggered. (The NSW has deteriorated a lot since the first fault a few months ago; Back then, temps would have to be about 30 for the NSW to fail, and in the teens to trigger LHM.)

Before I move the car on a cold morning, I know whether limp-home mode will occur: If startup RPM stays at or above 1000, no issues. If it is below 1000, limp home is usually triggered. (I wonder whether the drop in RPM causes the ASR, or if the ASR causes the drop in RPM?)

When the engine warms up, normally after driving ~3 miles, retsarting resets everything and the car behaves normally. (Interestingly, even if the car sits all day in the cold, and does not start in Park later on, ASR/LHM is not triggered; That only occurs after sitting overnight -- perhaps because the gunk in the switch has had more time to work its voodoo.) :)

I need to do mine soon, or have it done for me since the cost appears to be negligible.