ASR light - cause and effect - PeachParts Mercedes-Benz Forum

deanyel · #1 02-06-2005, 12:13 PM

re: 1994 E320 w/ASR

Puling fault codes is great stuff but it seems like the real art is in interpreting the information. My ASR light came on again recently and the car went into the limp home mode. I pulled the following codes, which I'm pretty sure were all related to the event.

DM LED - code 6 - Idle speed control faulty
DM LED - code 26 - upshift delay faulty
Pin 8 - code 8 - ISC indicates limp home mode
Pin 14 - code 14 - closed throttle position contact switch

So which code(s) are the source cause of the problem, and which are an effect of going into the limp home mode. I'm guessing that source problem codes are 26 (upshift delay faulty) and/or 14 (closed throttle position contact switch) and that codes 6 (ISC faulty) and 14 (indicates limp home mode) are just an effect of going into the limp home mode. Any thoughts on identifying and fixing the source problem would be appreciated.

Arthur Dalton · #2 02-06-2005, 12:42 PM

I sure wouldn't read a code 26 [ upshift delay for cat warm-up on cold engine/emissions code] into an ASR diagnoses..
.. and I think you may have a typo on the last part of your post - [re : 8 and 14]
CTP is the suspect

LeaUK · #3 02-07-2005, 02:23 AM

I would guess code 14 - if the car thinks it's in idle and the system detects the butterfly has opened it will trip a ASR light. Happened to my R129 regularly until I investigated and found it to be a damaged outer accelerator cable.

When the pedal was pushed down 30% or so, the outer would get 'stuck' (the outer was split) and then when the pedal was returned to no depression the idle switch detected idle - however the butterfly was open a fraction and so tripped the ASR..

You'll find may two cable tie solution on the SL forum. So, check your cable -assuming your model has one of course, apologies if it doesn't as I'm really only familiar with the R129 system.

Lea

mbdoc · #4 02-07-2005, 08:26 AM

3 of the four codes refer to a problem with the throttle body! Many times a problem with the accel cable being to TIGHT & not allowing the throttle to return properly. THERE is a micro-switch on the gas pedal linkage inside the car that MUST close before the throttle opens. IF that switch is bad OR not enough freeplay in the accel cable then will get those codes!

ALSO if the throttle body is BAD you will get those exact codes.

deanyel · #5 02-07-2005, 09:45 AM

That was a typo - that last 14 should have been 8. The 26 upshift code may well be unrelated - there was a period of several weeks when I had not checked the codes. The accelerator cable sounds promising, as does the micro switch on the gas pedal linkage. The problem happens in cold or cold/wet weather - not that it ever gets that cold in AZ - but it's clearly weather related. It's been doing it for a year at least - maybe six times in total. If the throttle body is failing it's doing so very slowly. It sounds like both accelerator cable and micro switch could be subject to weather conditions. M.B. Doc - is that micro switch available as a separate part? Thanks to all for the help.

Arthur Dalton · #6 02-07-2005, 10:22 AM

One thing to also check is look and see if there is floor mat/rug bunching up under gas pedal.. also sand and dirt. That restricts the pedal full up position and will show as a CTP/ idle switch contact code.
A look at the cable on the engine end is to pull the cable sideways and see if you have a 1/4 of slack... too tight on that end will also have the same results..that is adjustable.
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1D00YU6RY1G10M4URY&year=1994&make=MB&model=E-320-001&category=P&part=Idle+Speed+Contact+Sw

LeaUK · #7 02-07-2005, 02:39 PM

deanyel

mine also only failed in the cold (10degrees C) and was as exactly as MB Doc mentions. The ETA reported open but the pedal micro switch said idle - the ASR system reports fault accordingly and sets Limp Home!

Check the cable mechanism and adjust if necessary. There are some good instruction on www.alldatadiy.com on this procedure - well for the R129 model at least.

deanyel · #8 02-07-2005, 03:32 PM

I cut back my rubber floor mat around the gas pedal - it was a little tight. Accelerator cable appears to be OK - not too tight, about a quarter inch of play. I will try lubricating it also. I found the idle speed contact switch at Fastline with Arthur's link - but can't find it on the car. It's only $31 - so if it happens again I'll probably just replace that - assuming I can figure out where it is. LeaUK - before I subscribe to Alldatadiy - do you find it pretty helpful?

LeaUK · #9 02-08-2005, 02:07 AM

For my R129, where data is scarce, it's excellent. Not absolutely superb, but very good. There are wiring diagrams, how tos, rough price guides, all MB issued notices etc, etc...well worth the 25$ and 15$ renewal.

If you have the WIS, Star Finder and EPC it's probably not worth it, but I still use it often as simply a second point of view.

The more information I have the better when coming to fault finding cars.

Back to your issue. Has you car a quite complicated mechanical arrangement where the cable terminates at the ETA (electronic throttle accelerator). This is where the cable adjustment is normally done and in my car has several adjustment screws.

I suspect your switch is working and the ETA thinks it's butterfly is open - for whatever reason. Again mine was down to a broken outer sheath, check yours around the ETA. Search for my repair on the SL forum as there are pictures showing the simple repair and mechnical coupling which may or may not help!

Lea