500E limp home mode
 

The owner of a 500E I've been considering says that 4-5 times in the last 5 years, the check engine light came on, the car has gone into limp mode, that the diagnosis from the dealer has been very expensive, and that the parts have been relatively inexpensive. Does this sound like a computer problem? Have any of you experienced this more than once?

Tom

Hi Tom-

I'd suggest reviewing the associated work order's under each 'limp-mode' repair in detail ie review DTCs....this will provide a good indication for this particular car addressing your inquiry and provide an indication of a recurring problem/ weakness (if so)

We've had quite a few owners of the '92's and '93's with 'limp-mode' episodes (search). I've observed that the possible causes can take an extended time to narrow down and effectively address in the majority of the cases

...but you're correct in seeking perspectives on this topic 'cause 'limp mode' is never a good thing.

hope this helps
-fad

Oo-Boy, this could be expensive.... or not???

This is a Big weak spot in owning the otherwise wonderful 500E, sometimes the car could have this problem, or sometimes you may never see it. If you buy this example it's just a matter of time before it occurs. A exceptional Tech is worth his weight in Platinuim, find one to look at this particular car if you are thinking of buying it.

Funny, how you guys are talking about it,tonight I hit this gradual downhill light turn. Damn light came on so All i ever do is throw it in neutral,while its coasting I turn the igntion off and on ha ha its starts and light light goes off! while in motion I have this down to a science. I really drive my car hard sometime. I think in , say a month the light will come on at least 2-3 times.i have had actuators replaced,the control unit is updated. I think the early gen ASR sucks from my experience. But I dont want to spend 600 bucks to purchase a renntech ASR defeat switch. I think its a rip off for the price. I did purcahse one from PAD. That one sucke. Lame instructions, could figure them out so I returned it. As for me being a tech, I didnt even want to chance cutting into my OEM wire harness.


So Guys Who ever has the ASR light coming on at times. Live with. It sucks to say. I installed 2 throttle body actuators same **** still going on. All I ever do is hook up the HHT and erased the store codes. Maybe we can do a package deal with RENNtech. Or they can give us a internet price break. Just a thought.


Guido

There was a lengthy thread about this before...check the alt and volt reg before changing out modules and other parts, especially if the car has over 100,000 miles. A simple spike in power can trip a number of systems and false codes and throw the car in that limp dick mode.

Friggen' computers, sometimes I think I should get to get an old Hemi Super-Bee... talk about simple. Well, not really but there's something to be said to that effect in this case.

Tom, sounds like a huge bargaining point for you, if you care to tackle the problem. It is fixable as others can attest to.

Hoo boy, I just lived through this one. My car is fine now. No more ASR/Check Engine lights. But it cost me nearly 3K to get there. Much of that money was wasted on misdiagnosis. I learned there are more than a dozen inputs and/or faults that can trigger this event. This is compounded by the known problem with disintegrating insulation on the engine wire harness. What you NEED to find is a tech with access to the Mercedes factory diagnostic system who has the patience and access to your car enough to track down the fault. In my case, the first diagnostic unit that was used to read the stored fault codes was insufficient. It only showed up as a live fault on the Mercedes unit.

Check the thread I started about my car in the tech help forum. Do a search for ASR/"limp home" mode. In my case it turned out to be a failed transmission shift position sensor. I wasted my money replacing the throttle actuator and the Electronic Accelerator Control Module. Spend your money on diagnosis first. But on my car it could only be found when the sensor had failed enough to trigger the fault pretty much whenever I drove the car.

The tech who helped me solve my problem printed out a block diagram of the engine management system from the service manual. It shows the many inputs that make up the system. It is worth tracking down; it gives a good indication of how expensive it can be to just try plugging in components to fix the problem. By the way, I have a serviceable throttle actuator and EACM if you want to buy them!

HI MARK GUIDO HERE. LISTEN EMAIL ME. MY DAMN ASR ASR HAS BEEN COMING OM MORE FREQUENTLY. IVE BEEN DIAGNOSING
I HAVE SOO MANY DIFFERENT CODES, IM CURIOUS ON THAT SENSOR YOU JUST REPLACE WHAT IS THE CODE AND WHERE IS THE LOCATION, WE DIDNT DO AT SOUTHBAY DID WE.

PLEASE EMAIL ME



THANKS GUIDO

Yet another 500E in the neighborhood that I have looked at has an ASR defeat switch. Does this solve the problem?
Tom

I'm not sure if it will solve the problem but it might.

What usually happens with this whole ASR issue is that you are accelerating at a full rate and for no apparent reason the ASR system will malfunction and send the car's computer into "Limp mode". That means the engine is still alive and will get you home, but with only about 1/3 power compared to normal, you have to floor the accelerator pedal to get to normal world speeds, not good.

From what I understand, sometimes and sharp left/right hand turn while going uphill or downhill can activate the limp mode as well.

I have only had it happen once with my car and that is when I was playing around and had the front ABS sensors disconnected so I could smoke the tires and lay some rubber down. I hit redline in second gear and the car just immediately went into limp mode, needless to say I thought I broke something! I coasted to a stop, turned off the car, waited 10 seconds and all was well again when she started up, but my hooligan behaviours where done for the day! Some cars are more prone to have the L/M (Limp Mode) issue come up, not sure why?

Ask the PO for some details about what triggered the event if you can.

Good Luck

The "Limp Home" mode can be triggered by many events, not just an ASR fault. In my case, it was the shift position sensor, aka safety neutral switch, part no. M000-545-62-06.

asr/limp home mode
 

There is a thread here somewhere posted by a member in Europe. It refers to the the transmission shift position sensor.
Basically it said to put the car in 2, and floor the throttle. At abt 4500rpm the ASR light comes on and the car goes into limp home.
Replacing the part as Mark did seems to cure this problem.

Guys

My car had done the 'limp' mode back in Dec and I finally had it fixed , a $10 stop lamp switch was all it was, part no. 001-545-01-09. According to my servicing dealer, when this part goes it controls many of the other functions thru the computer and can cause like the ASR lite to come on, among others....Also, in my 130,000 mile car, the alt. was on the way out and the volt. reg. had a nice groove worn into it...so less than $400 to fix and I have a new alt that'll keep me going for another 130,000 miles. All better, whew, I was expecting the worse...from what Mark went through.

So, in short, check out the small things first if your car does the 'limp' mode thing...doesn't necessarily mean a large dollar fix or should chase one away from buying a 10 year old 500E. I think we owe a bit of thanx to Mark on his trials and tribulations with his (car's)'limp' problem and being so forthright with his findings...unfortunate for him he had to spend un-necessary big money on fixing his car, and fortunate for us we have his experience to work with on this type of problem.

Donations cheerfully accepted!!
 

Thanks for the nod, Jim. Of course, that's the whole point here, isn't it? I've saved a lot of time and trouble here as well. And remember guys, if your car is going into "limp home" mode on full acceleration, there is a problem. It isn't normal that it should kick in at all except by mechanical or electronic fault. If anyone can help me post that block diagram, let me know. I can scan it but if I attach it at permissible res, I don't think it will be readable.

Engine Management block diagram
 

is probably the same as that posted on my web page. Click on Menu #1, Engine Management Systems. All of the inputs from the various sensors can be seen.

Glad you got it fixed. Helpful info that you posted.

After further conversations with current owner, he said the car did not go into limp home mode, but when the check engine light came on it just ran roughly until the repair was done.
Tom