I have a problem with my 1995 SL500 vin WDBFA67E6SF113784
ASR Fault light comes on and the car goes into limp mode when the car is cold. There is a pattern though. I let the car idle in the driveway until the water temp gage read 40 deg C and the system failed as soon as I tried to drive it. I tried again with the car at 60 deg C and the system works fine. I have taken the car to two independent Mercedes shops. One replaced the ASR module. The other changed the Anti-lock module with no effect. both shops said they checked the brake switch.Does the ASR system useeither the wateror transmission temperature sensors?

 

I wonder how much they charged you for two ECU modules?
Why do garages immediately suspect the ECU is wrong!
ECU's are mega reliable so long as they have not got wet.
I guess its because they have little understanding of how such devices work.
I now have to consider that the ECU's may not be the correct type etc but let us assume that the ECU's were OK, and that the new ones are equally sound.

However, since you state the car is going into "Limp" it is likely a code is being set so you need to get any codes read.
Didn't the garage do this before changing the ECU's? Maybe they didn't advise you.
Any codes will give further investigation some direction.

If no codes have been set the circuits must be passing startup (boot) checks and the issue must be one which only becomes apparent once the vehicle moves.
This could easily point to a wheel speed sensor but can't think why this is setting "Limp".
Such a fault would illuminate the ASR warning light but why put the vehicle into "Limp"?
Are you sure it is in "Limp"?

I'm also confused regarding the ABS. You don't state that the ABS warning light is On or Off?
I'm assuming that it may also be On since they changed the ABS ECU although you don't state that the light is on.

Wheel speed is a common signal to ASR / ABS / ESP (if you have it) / Trans etc.

Had any work done on the wheels recently.
Changed, Balanced, Puncture repair etc?
I'd have a very careful look at the wheel speed sensors. Front first.

Oh and just to the eliminate another possibility are you sure that the battery is good? 13v approx engine off, 14v+ with engine at idle. Many of these circuits are voltage sensitive.

Good luck.
Stuart

 

hi i feel your pain here ! last week i had to change the front ball joints, this was done with my trusted friend and me as his sidekick (not so trusted ) As soon as i drove out of his garage i noticed that the breaks were acting funny, as in making a kind of grinding noise, which sounds to me that the ABS is kicking in prematurely, since then the ABS and the ASR lights have been lighting up unremittingly. But this is the strange part when the lights are on the breaks seem to work fine and when the lights are off the breaks seem to be hyper sensitive i.e i am feeling it grinding. All this is not much help to you but if someone can help you out maybe you can pass on the info

 

sorry that was meant to be intermittently not unremittingly

 

Thanks everyone for responding. Let me address Mr.? snanceki's questions and give some new info. The repair shop situation went like this. Shop 1 tried and sent it to shop 2. Somewhere along the way the ASR and ABS modules were replaced with used parts. They have had the car for 5 weeks. Shop 2 said they fixed it but when I went to pick it up the bill was for $1710, $910 parts and $800 labor. As stated the problem persisted. I told shop one manager that that I,ve given up on you guys and I was not going pay anything forNOT fixing my car.The car is now in my gargage.

Both shops talked about reacting to codes but I did not get any details.

I use the word limp because it appears in other posts about the problem. "Limp"refers tothe gas peddle needing twice as much travel to get any increase on RPM. once there, the engin seems to have the usual power.

No work has been done to the wheel brakes tires etc. The pressure is equal all around.

Only the ASR warning light has illuminated, never the ABs light

I have turned off the ASR systemand the light in the speedometer comes on.When the system failsthe ASR off light goes off, the ABs warding light comes on and into limp again,

Shop one said they checked the brake switch and the wheel speed sensors.

I still have to check the battery voltage.

I think the engine temperater thing is a clue. Why would it work as long as the engine is ar 60 deg C or above.

Thanks again for any help

Mike

 

ASR is linked with the engine ECU / EA Electronic Accelerator since engine power is modulated under certain ASR circumstances.
Unfortunately I am not familiar with ML and am not sure whether the EA is totally "fly by wire" or just partial. I suspect it will be full FBW.

I believe that the key to this issue lies somewhere in your statement and especially the final sentence:

Quote: I use the word limp because it appears in other posts about the proble. "Limp" refers to the gas peddle needing twice as much travel to any increase on RPM. once there the engin seems to have the usual power.

"Limp (Home)' is a specific condition and is initiated by the engine ECU to get you home when certain electrical engine components fail. It is designed to prevent you being stranded by the roadside. Yes it makes the accelerator and transmission work in a very strange way.
When Limp us set it illuminates the Check Engine Light CEL although of course other faults can cause the CEL to illuminate.

I'm thinking that there MAY BE an EA issue. However I'm not that familiar with this issue so if presented with the problem on my own car I would start by understanding what, if any, codes have been set / return after a reset. Codes do not tell what is wrong but they point you (if present) in the right direction.

You need to have the car scanned using MB Star SDS diagnostics...not just a regular OBDII scanner.

Get the codes and I will see if I can help any more. Please advise outcome once you resolve this issue.

So what did the shop(s) say when you didn't pay the bill?

Stuart

 

The symptoms that you describe is the identical to what I have, in my situation I had check the codes and its outcomes with problem in OC2, did you check that?, I relay on Snanceki advises, so check the OC2 for codes.

 

OC2?
Stuart

 

An update.

The battery checked out at 13.2v at rest and 14.2 while charging.

Also I reported that the ABS module had been changed. Actually it was the throttle control module.

 

So long as the 13.2v remains steady under cranking all should be OK voltage wise.

OK so it was the throttle control module rather than ABS module. However not quite sure to what you refer.

The EA consists of the pedal (potentiometer) and the butterfly valve (servo motor). The two are connected via the engine management ECU but maybe there is another box which I have overlooked. I need to cross check in WIS.

Stuart