ASR problem from a new owner
 

I just bought a 1992 500SL which worked great during the test drive. Now that I own it, the ASR light comes on, it goes into limp mode and the engine will stall.
I've read the treads, trying to narrow the problem down. One sympton is that it may only be occurring when the car is driven at low speeds, such as in traffic. If I can be aggressive with the throttle, no problem.
The other feature to my problem is the fact it stalls. As the dealer pointed out, that shouldn't happen in the limp home mode as it would be a saftey problem.
The car is now at the dealer, he has not found any codes. He's searching.
Anyone have any good ideas of where to look first?
Jim

Do a search on "asr light" and you'll see a lot of posts on this.

Mine was caused by a faulty brake light switch.

Wonder why no codes were set? I understand that some malfunctions have to occur 3 times before a code is set, but I wouldn't expect that from a problem like an ASR system malfunction complete with limp-home mode.

I've had the light come on many times, one would have thought it would have set a code but they report it hasn't. Without the code, they seem to be lost.

You want to get a code as soon as the thing craps on you.
Intermittent ASR are usually brake switch , but by the time you get to the scanner , it has erased.
The car has Flash code retrieve and you can make a simple tool to get the codes yourself from the EA module [ this is where you will find an ASR code on 129.066]
Do a "code tool" search . The EA access on that car are at pins 1 and 3 for power and pin 7 for EA/CC /ASR codes.

Thanks. The dealer said he'll spend up to $500 in time looking.
If he fails to find it, I'll do what you said rather than spend more time for him to search.

Arthur,
I could swear I read that once a code is set, it's only erased after a rather large number of normal start cycles have elapsed -- like 100? Not true for ASR fault codes?

Brake lamp switch codes can be cleared in no time..

I was unclear in my question. Here's what I meant to say:

How long do fault codes stay in the computer if they are not manually cleared?

I had understood that the computer itself has the capacity to clear certain codes if a certain number of normal operation cycles (i.e., engine start/stop) occur, so that a one-time, transient fault code won't stay resident in the computer forever.

Is this accurate?

From what I've personally . . .
 

seen, anytime there's a "light", there's a "code"! And you are correct, some codes take a number of occurances to cause a light and a certain number of "trips" to clear. The definition of "trips" has changed as the models change but it's not just engine starts and stops but involves engine rpm and length of time.

On the other hand "running" problems can instantly light the CEL but do take time (# of trips) to clear. For the DI module it takes eight (8) events to trip a CEL.

For this module a “TRIP” is defined as:
1) Engine running for 5 minutes or more,
2) Tachometer greater than 700 rpm,
3) Speedometer greater than 2.5 mph,
4) Engine shut off for 30 seconds or longer.

Can't see how an ASR problem would not generate a code or two. There's a code for the brake lamp switch as you probably know.

It's probably the ETA...
 

Considering the age and model of your car, it's probably time for a new ETA (electronic throttle actuator). My car has the same problem but usually lights up the Check Engine Light (which I have come to ignore for now). It will take a few more paychecks to replace the ETA and everything should be fine by then.

I forgot to add that it is possible that the bowden cable is worn out and the plastic sheathing has crumbled away.

Good luck. :)

The drive cycle code clearing is a memory feature for any soft code.
But for intermittent codes , there has to be 2 back to back trips of the exact same fault for storage . However , if the first trip registers a fault , it is pending in the memory. If it does not return the next trip, it does not get stored, but erased. That is why brake lamp sw codes are hard to find.. but is you get an ASR fault due to a sw failure , you can get the pending code from the module even though it has not been stored. It is a pending code awaiting failure on the next trip to get stored. But it is still there..
Many Tech with ASR complaints just change the B/Sw before proceding to the ETA b/c of the high fail rate and difficulty of catching the intermittent poor contact of the sw. You can pump a bad b/sw many times and not see a failure , but it can also fail 5 times in a row.. it is a mechanical contactor, highly used switch...
You will notice that his problems were at low speeds and stop and go.. good probable of sw failure due to activation. On the same note , you notice he was having stall problems, indicating a probable ETA.. My first shot would be go with the sw and clear out any memory codes ..
As I mentioned in the earlier post, the EA/CC w/asr module is where one wants to look for possible stored or pending codes
The CE MIL lamp has nothing to do with these codes as the CE is activated by emmissions related codes
The Stop Lamp codes are #2 and #6 of the N4/1 module and do not trip a CE lamp........

If the ETA is going bad . . .
 

. . 'bad', you will get codes in the Diag (pin 19), EA w/ ASR (pin 7) and ABS w/ASR (pin 6) Modules. My case was typical for what happens in a V8, "S" class car. Check out Menu #24 to see what codes were set.

The EA module as well as the DM have multiple levels of fault storage; Active, Registered and Stored. Here's what they mean.

Active Faults - These faults are detected while the car is running at idle or speed. They represent a component that maybe or is currently failing. These codes cannot be erased. They are only meaningful with the ignition on and the engine running so DTCs found in this system with the "key-on-engine-off" usually have no meaning. Sometimes it shows a components not present on the car as failing so these codes do more to confuse than to serve as a diagnostic tool. But if the code persists, and the CEL lights, then it indicates a bad component but not necessarily the DTC that stated!!! Thus the confustion.

Registered Faults - These faults are recorded in the temporary memory of the of the car's ECUs. This temporary memory records the the fault indicating that it has occurred and is continuing to occur but it hasn't exceed the preset number of times to make it a Stored fault. When that certain number of failures has occurred, the fault is now moved to permanent (Stored) memory and the CEL lights. Some ECUs that have internal fault registers, the CEL may stay on after the Stored or Permanent fault has been erased if another occurrence of the fault has happened since the 'permanent' fault was stored. To extinguish the CEL, you should always erase both Stored and Registered faults.

Stored Faults - These DTCs are sometimes called 'permanent' codes. These faults are recorded in the permanent memory of the car's ECU and are the main cause of CEL light. They have been generated because the fault exceeded the preset number of times set up for for that function. These DTCs can (and should) be erased.

Thanks, Jim and Arthur! Excellent information, well presented.