I was wondering if I might pry into some genius.

I was recently having an ASR/limp-home mode problem on my 94 E420. I have been trying to eliminate what is not the problem, and finally replaced the stop light switch underneath the dashboard for the brake pedal.

I then took the car out for a spin, and hopped on the freeway, expecting the ASR light to come on and feel the limp home mode drop in. But instead of that happening, all of the dash lights in the gauge cluster lit up instead, then popped off when I used the turn signal, then back on again. I stopped the car, turned it off, restarted, took off, and the lights came on again, but no limp home mode whatsoever. So far.

Any thoughts to an explanation?

 

Hi,
You've been behind the dash and all of a sudden the symptoms have changed. Yes?
If so it appears that something is loose.
The Turn Signal bit potentially indicates a poor earth.
No idea where the earth points are on your car but you need to look around for any wires intentionally bolted to ground and make sure this junction is sound. Wires are usually brown but could be different on your model. Often on the top of the tunnel or the steering column bracket or adjacent bodywork

Liml Home isn't normally initiated by ASR but it certainly impacts engine performance by reducing engine power and applying appropriate brakes.
Exactly what do you mean by Limp Home....the engine will only pull 3000 revs, strange if any gear changing and car can only manage 30 mph (ish)? or something different.

Not sure I have a clear idea of EXACTLY what ithe symptoms are.

If the "Limp Hme" (your words) resets with an ignition OFF/ON then the EMS thinks all is OK when the "startup" checks are done and something subsequent to startup triggers the fault.

Is your cruise, ABS, ESP (if you have it),speedo etc working? Usual ASR problem is a faulty speed signal but this also impacts other systems.

Brake switch is usually associated with inop ABS, Cruise and Auto selector lever.

Maybe you can clarify some points.

Stuart

 

Thanks for the reply Stuart.

My car is missing the cruise control selector arm. So I don't have the cruise control option. The turn signal, gauges, and everything else on the car still work regularly, although this morning the limp home mode kicked on again twice on my short trip from the chiropractor to my house.

Limp home mode (to my knowledge) keeps the car in 2nd gear as long as a foot is on the accelerator. Once I release my foot, the car downshifts. The RPMs never go extremely high, and the car doesn't shudder or rough idle. Happens to me on the freeway and car can still go 80mph until I get off the road.

I feel like the Limp Home mode kicks on if something goes awry shifting between 2nd and 3rd gears on the auto. If I go gently on the pedal it doesn't seem to be affected, but it seems if I am stomping the pedal (just to accelerate quickly) the car imbeds in 2nd gear for take off, but instead of shifting up to 3rd, LH Mode kicks on instead. Could be related or I could just be nuts.

LH Mode is reset by turning the car off and restarting, but doesn't keep LH Mode gone for long.

Car does not have ESP. ABS and Speedo, Tach, and other gauges still working normally.

 

Alternator was replaced and for the first time, I enjoyed driving the car without any dash lights on. All problems appeared fixed, and they even got the Check Engine Light to turn off which had been on since I bought the car and was supposedly untraceable.

ASR light STILL COMES ON and car STILL GOES INTO LIMP HOME MODE.

No matter how much you buy for a girlfriend, she always asks for more.

Suggestions welcome.

 

All you ever wanted to know about ASR maladies, but were afraid to ask:

http://pages.prodigy.net/jforgione/MB_asr.html

I had similar problems with my '93 400E [W124] and ended up replacing the throttle actuator [expensive, around $1,400 as I recall for the part] and finally the neutral safety switch, which wears and the contacts corrode\over time. I would start with the neutral safety switch [inhibitor switch] and see if that helps.

The other component that can go bad is the ASR/Cruise control ECU. If you eventually find that this item is bad, I have a "guaranteed good" used one. List on that item new is around $2K.

Good luck with your problem.

JR

 

Sorry for long delay in reply.

Looks like you may have multiple problems.

I'd sort the Limp Home issue first since by definition this is the most important issue.

First step decide if any codes are set / reoccur once cleared, as a starting point. This may add valuable data but your car is pre OBDII so code info is less all encompassing.

If I was to guess (missing out this important step) I would guess at the Throttle Actuator is bad BUT I advise against changing parts without going through an effective process of elimination. including ensuring Service history up to date,

Problem with replacing the Throttle Actuator is that they are quite expensive and if not the problem you won't be impressed.

However the Throttle actuator also interfaces with the ASR and if the Cruise had a lever I'm sure you would find that that also was not working.

Water ingress into the TA is a relatively common problem.

An alternative strategy is to take the TA apart to see if water has got in. If so thats your problem.

Stuart

 

I'll make another appointment to have the fault codes read at the dealership. My mechanic doesn't think the TA is bad, but he doesn't have the equipment old enough to read the codes.

IS ANYONE INTERESTED IN BUYING THIS CAR? It really is a nice ride for someone who wants to take care of this beauty.


Thank you all for your responses. The process of elimination continues...

 

Your mechanic can get an interface cable that will allow an OBDII compliant reader to read codes from a 38 pin round diagnostic connection...

An example: http://www.obdtoolstore.com/shop/pro...products_id=80

There is no excuse for a shop that works on our cars to not have the proper equipment to do the job... IMHO.

Good luck, as I am not sure the dealer is going to be happy to provide codes to enable another shop to do the work.

As far as getting rid of the car goes, only you can make that choice, but once this problem is solved you may well once again have a great car...

Lastly, don't forget about the neutral safety switch; that item often does not show up in a d/l of codes, mine didn't. The shop foreman at my local dealer remembered it because the dealer had to buy back an E420 similar to yours under the "lemon law" because they could not find the problem. It turned out to be the NSS. Mine looked like the AC evaporator box drain tube, or something else, must have dumped condensate/moisture on it for years... really corroded.

JR