Yes another ASR problem; '94 S500
 

First of all, let me say that I have read EVERY ASR thread last night, about 11 pages full! Try that for bedtime reading! I guess that if you own a Mercedes, you will at some time get that problem!

My ’94 S500 ASR light started to come on about three (3) weeks ago. At first, I just could ‘fix’ it by turning the car off for 5-10 secs and then re-start.

Slowly it’s been getting worse. About 3 days ago, it wouldn’t reset by recycling the ignition. I drove the car for 5 minutes; when stopped at a red light, re-cycled the ignition. It went off and stayed off as long as I drove the car.

Symptoms:
1) Only occurs when the car is HOT, not warm.
2) The ASR light comes on, tachometer indicates 1000 rpm but can drive the car even though it’s in the Limp-Home (L-H) mode.
3) If the ASR is on, drive for 5 minutes or so, stop, re-cycling the ignition and the ASR light will go off and STAY off until I stop the car and let the heat build up in the engine compartment. If I start the car, the ASR light and L-H mode will be active but it can be ‘reset’ by driving it for a few minutes (even if HOT) and recycling the ignition.
4) It NEVER comes on while driving.

DTCs:
Yesterday I dumped the codes with an AST Retreiver Scanner:

Base Module: No codes
Diag Module: REGISTERED CODE only - Code 6 - - ISC faulty
EA/CC/ISC Module: Code 2 - - EA/CC/ISC or Contact switch M16/1s1 or Stop lamp switch.
ABS w/ ASR Module: Code 30 - - CAN bus to EA/CC/ISC faulty.
LH-SFI Module: No codes.
DI Modules: No codes

Note that the CE light is NOT on. The DM module has a registered code but no ACTIVE codes.

I removed all of the modules in the F23 box, removed the box frame itself, and inspected all of the wiring to the connectors especially to slots 4/5 (ABS w/ ASR) and 6/7 (EA). All wiring was ‘solid’.

Using an ohmmeter, the CAN bus was checked. All readings ok: 120 ohms across the bus and continuity to all modules on the bus.

After reinstalling the modules, which had all cooled down, the car was started, NO ASR lamp. Ran perfectly.

Drove it for about 20 minutes, parked it in the sun (yesterday in SD, it was 95degs). About 1hr later, I came out and started the car, ASR on and L-H mode. Performed 3) above and light went out. Parked in the garage; let it cool down overnight. Just started it ‘cold’ this morning, everything ok, no ASR.

I have my opinion as to what’s I think is bad, but would appreciate your opinions and what would you do next?

Well, its one of 3 things. The EA, the EGAS cu or the harness. Have you run the pin tests on the EA's refernce potentiometers? My gut feeling here is the module itself is bad, however I've had a few 140 cars that the EA was "killing" EGAS.





Joe

most common for those codes is the EA...

Joe p, when you say "EA". . .
 

reference resistor, do you mean the "TA", throttle actuator that has the potentiometer?

mnstang, I assume you mean the EA Module itself??

My opinion is that it's the EA module itself. It has all the symptoms of having a heat problem. There's no other codes set, and the 'clincher' is ASR code 30 that says it can't talk to the EA module. And that makes this problem occur. Am I correct?

Never had this problem and basically in the dark. Your knowledge and experience is appreciated. If it is the harness, would it only do it when 'hot' as opposed to all-the-time?

Next week, I'm going to swap it with another EA unit and see what happens.

sorry i wasn't more specific... electronic actuator (basically the throttle motor sitting on the intake).
there are a couple tests that you can do for this, but with an intermittent problem like this, they usually pass the tests when you test it.

Hi Jim,
I just posted another ASR problem with my car under:
" ASR light and no power!!!! " before reading your post.
Am I having the same problem you are heaving?
regards,
Sab.

Well, the 'other' car . . .
 

doesn't have ASR, so that ended that test before it began!

In the mean time, I measured made some more measurements, and, no matter what, I still get the same codes as posted above, no additional codes.

But today, I wasn't able to make the ASR light go out by performing (3) while to car is hot. But if it cools off, (engine hood up and cools to ambient temp), the ASR light is off when started. So that's still the same.

Am tempted to buy a used E-Gas module to test. May just do that.

Update: 9/12/03
 

Was able to find a compatible EA/CC/ISC [N4/3] module to test in my car. Well, it worked for a while! Same thing after 6 trips or so: If the car is stopped after high speed driving and then into stop-go traffic for 10 mins or so, ASR light comes on. The engine heat builds to 100C or so when the key is switched on.

It was NOT the EA/CC/ISC module even though the codes seemed to point to it. Re-check the codes and they are still the same as reported previously.

Well, as joe p said, there’s two things left and my money is on the ETA, Electronic Throttle Actuator as the ‘bad-guy’! There’s not a hint of a DTC for the ETA so it just frosts you or should I say, burns you!

But until it’s fixed, I performed a little trick that was mentioned in one of the many ASR posts: connect pin 6 on the Diag Connector (38 pin) to pin 1 (ground). This forces the ASR module in the diagnostic mode and it returns the car to a normal accelerator pedal. In fact, in a short drive, the car seemed to have a bit more power. Probably my imagination. Of course you have NO ASR!

But now the ASR light is on. So to kill that, insulate pin 29 on connector 1 of the ABS/ASR [N30/1] module by using a strong but thin tape. The MIL signal comes from this module and lights the ASR lamp located in the IC. The ASR light will still light when the ignition is turned to position 1 but will go out after the car is started. No chance of it coming on. I don’t recommend this as a permanent fix but this will kill the glare of the very bright orange ASR light without pulling the IC and removing the lamp.

Now, I need to tackle the ETA and see what’s up with that unit. Any suggestions on how or where to look/measure for problems?

Update: 9/13/03
 

I got a chance to drive the car and I don’t think it was an “imagined”; the car definitely has more power with the ASR disabled especially at 1500 – 2000 rpm.

Comment regarding the ASR light: the ‘mod’ only allows the light to momentarily ‘flash’ in position ‘1’ but that’s no big deal. It does stay 'out'.

Is there a better way to disable the ASR???

Update: 9/21/03
 

Yesterday, the car went into the limp home mode when first started. And it wouldn't come out! So the 'disabling' of the ASR worked only temporarily (pin #1 to #6).

Tomorrow, the ETA and cable harness will be inspected/tested and most likely, the ETA replaced.

Jim,

Thank you for your continued updates, I know this will be something that nearly everyone with ASR will experience eventually so it's good to get the info up front. Good luck and I hope the ETA takes care of it.

Update: 9/22/03
 

Removed and replaced the ETA today: took most of the day since I really didn't know how-to-do-it!

Attached a picture of the 'beast': it's some kind of assembly!
http://pages.prodigy.net/jforgione/ETA_overall.JPG

First, must remove the MAF and 'rubber' double-tiered gasket that holds MAF and connects to ETA. After that the hardest part is to get the ETA out from in between the intake manifold ports.

The most difficult part was the small spring that serves as a tensioner to the linkage. It attaches (someplace) on the intake manifold and provides tension on the linkage: the #!(#%^% spring fell off and it literally took about an hour to get it back.

Before removing the ETA, the codes were read: picked up one new code in the EA/CC/ISC; code 3 ETA actuator [M16/1] faulty.

One key point: with the OLD ETA, I could NOT reset the codes in the EA/CC/ISC or ASR: ie, after using an AST scanner to reset the codes and recycle ignition key, the codes would immediately re-appear without starting the car. According to one of my MB manuals, that indicates that the ETA is bad.

After replacing with the new ETA, all codes were reset and would stay reset. Started the car and it ran fine. Will check for the next few days.

I will take it apart in the next few days and see what 'goodies' are in there???

ASR Problem
 

May I make a suggestion that will work for most Electronic problems that are temperature related.

Buy a can of Cold Spray as used in Electronic test & repair.

It's used for locating thermal intermittent electronic component problem, PCB cracks, and cold (dry) solder joints.

If you, one at a time, use the spray on the suspect components it will allow you to isolate the problem item by cooling it down to it's starting temperature.

It is available from nearly every Electronic Hobby shop's and costs very little.

Get a big can as when you think you have found the item you can cycle it a few times to be really sure.
Also when electronic components are inside a metal case you need to reapply a few times in sucession as it will take a while to "Sink" through the casing.

Have used this technique for many years and found it foolproof.

Regards

Mike

http://uk-commerce.com/temp/mb_banner1a.jpg

Good info! I have learned a lot.

I have intermittant (i.e., once a year) problems with my cruise control cutting out and going into LH mode, which then resets by restarting the engine. Since it's such a rare event (so far!), I have decided to wait until it inevitably gets worse. When it does cut out, it only happens after I've been cruising for a while, which makes me wonder if it's a heat-related problem with the TA.

JimF: Did your cruise control work normally before you replaced the TA?

And thanks a lot, JimF, for keeping us up to date on your progress! Good luck!

Steve

It's been an interesting . . . .
 

and great learning experience. From what I read in the many ASR posts, there's certainly a lot of ways that it can act up!

Steve; re CC: No problem! If the ASR light was 'out', then everything worked perfectly including CC. And my ASR had never come on while driving, only after sitting a while. I do think it's a heat related problem in the ETA.

Mike: as a design EE for 41 years for a large aerospace company, that technique was (and is) used a valid diagnostic tool. Since we designed large (8" x11") pcbs with literally hundreds of ICs on board, it worked quite well when you could spray directly on the IC.

But in this case, trying to cool that large metal assy with a spray can would not work especially since it is mounted to block via intake manifold. Because of its large mass and thermal inertia, trying to dramatically change temperature of an internal component through the metal 'skin' is akin to changing the ocean temp with a glass of hot water. :( Of course, if the case can be disassembled (left and right side) while insitu, it would be a useful tool. If it could be 'bench-tested' with sides off, spraying would be a great tool! Tnx for the idea.

That was the original ETA so it's at least 9 years old. Since it is subject to tremendous engine heat, it makes sense that it would be a high failure prone part. I'm looking foward to disassembly the part to see how it's constructed.