ASR Warning Came On ... Now What - PeachParts Mercedes-Benz Forum

cpiad · #1 09-11-2006, 09:06 AM

I was driving home from dinner last night ... and after completing a right turn at normal speeds ... the ASR warning message splashed across the instrument panel message area. The engine continued to run at nominal idle, however I could not throttle up the engine and there was no propulsion to the rear wheels. I pulled over to the extreme right apron of the road, out of the way of traffic, and turned the engine off ... waited about 30 seconds and restarted the engine. The ASR light did not come back on ... I drove about 4 miles to home without incident.

Are there any suggestions as to how I should proceed to diagnose, correct, remedy the problem? I have to use this car to ferry my 86 year old mother back and forth across Alligator Alley and I can't afford to have it break down on that desolate road with an old lady in the car.

I've got a 1996 E320, with 57,000 miles on the odo. I bought the car new and my maintenance has been and continues to be impeccable and beyond that which is called for in the owners manual by MB. The only other thing that has required action beyond preventive maintenance is a CEL light of P170 which appeared two weeks hence, which I tracked down to a "potential" MAF failure. I removed the MAF, cleaned the sensor plate with a non-residue/high quality electronic component spray cleaner and dried it with compressed air. I cleared the CEL code and replaced the MAF ... and the CEL has not come back on (yet).

I would appreciate any and all assistance. Thank you.

Gilly · #2 09-11-2006, 09:36 AM

Sure does sound like a bad throttle motor to me, I suppose it could be the microswitch in the gas padal too, but probably the throttle motor.
Need to check for stored codes in the ECU and ASR
Gilly

Arthur Dalton · #3 09-11-2006, 09:58 AM

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Check tire pressure/size for uniformity...

Gilly · #4 09-11-2006, 10:23 AM

Arthur, I thought of that too, or maybe a wheel speed sensor, but I don't think these faults would cause limp-home mode.
Gilly

Arthur Dalton · #5 09-11-2006, 11:31 AM

Quote:

Originally Posted by Gilly

Arthur, I thought of that too, or maybe a wheel speed sensor, but I don't think these faults would cause limp-home mode.
Gilly

I thought of that too, but b/c it is in a turn , it may trigger limp.
Just a first check I would do........if for no othger reason than to get it out of the diagnosis.

Gilly · #6 09-11-2006, 11:34 AM

Sure, makes sense to check it, or maybe a case where the owner just rotated tires or had to replace a single tire for some reason, or put the spare on it. Best course right now, besides the few things we've mentioned, is to get it checked for codes.
Gilly

Arthur Dalton · #7 09-11-2006, 12:03 PM

Quote:

Originally Posted by Gilly

Sure, makes sense to check it, or maybe a case where the owner just rotated tires or had to replace a single tire for some reason, or put the spare on it. Best course right now, besides the few things we've mentioned, is to get it checked for codes.
Gilly

I agree.. that is why I mentioned tire size along with air pressure.
Codes are next step and would not be surprized to see a brake lamp sw fualt in the codes memory .......

cpiad · #8 09-11-2006, 12:15 PM

Quote:

Originally Posted by Arthur Dalton

<>

Check tire pressure/size for uniformity...

hmmmm ... will do ... right away. thank you much.

cpiad · #9 09-11-2006, 12:18 PM

Quote:

Originally Posted by Gilly

Sure, makes sense to check it, or maybe a case where the owner just rotated tires or had to replace a single tire for some reason, or put the spare on it. Best course right now, besides the few things we've mentioned, is to get it checked for codes.
Gilly

No spare on it ... just normal tires/wheels. Will check air in all ... then put my OBDII code reader on it ... may have to get back to the forum tomorrow .. chaos in my house today ..

my wife is home ... honey do this and honey do that ...

I'll see what I get from my code reader and report back to the formum ASAP. thanks you guys.

cpiad · #10 09-11-2006, 12:22 PM

Quote:

Originally Posted by Gilly

Sure does sound like a bad throttle motor to me, I suppose it could be the microswitch in the gas padal too, but probably the throttle motor.
Need to check for stored codes in the ECU and ASR
Gilly

Is there another term for "throttle motor." This is an "old" straight six 104 engine ... not a "throttle-by-wire" like the new ones. Pardon my ignorance if I don't understand the terminology. Would appreciate any additional info on the "throttle motor" and its location. I am assuming the m/switch is in the vicinity of the gas/throttle pedal. However, I realize that I need to draw the codes out of the car ... or try to first. thank you.

cpiad · #11 09-11-2006, 12:25 PM

Quote:

Originally Posted by Arthur Dalton

I thought of that too, but b/c it is in a turn , it may trigger limp.
Just a first check I would do........if for no othger reason than to get it out of the diagnosis.

Thank you for telling me about "limp home" mode. I didn't seem to be able to crawl anywhere, much less limp, when the ASR warning splashed across the visual annunciator ... is there something special one does to "limp" home? My recollection was that I applied pressure to the gas pedal and there was zero forward response ... almost as if the throttle and transmission were completely disengaged ... but with the engine at nominal idle ... ok ... I have to pull the codes ... or try to. thank you.

cpiad · #12 09-11-2006, 01:59 PM

Gentlemen ... after I went AWOL from my Commanding Officer (Wife) ....

I checked the air in all the cold tires ... they were all down 3 psi uniformly. I filled them all to factory cold air pressures.

I hooked up my code reader ... and there are no codes stored in the ECU. I hooked up twice and restarted the engine just to make sure there were no connection glitches. The code reader went through its diagnostic thing and did everything it is supposed to do ... but there were no codes to read.

I'm left perplexed ... and concerned about the reliability of this great car ... heretofore it has been Mr. Reliable ... any more ideas?

Arthur Dalton · #13 09-11-2006, 02:06 PM

I would still suspect brake lamp switch.. very common and this is one of those "Change it" recommendations as it takes longer to catch it faulting than it does to change it. [ cheap part] One of the few times I will try a new as part of diagnosis [ the other being an OVP relay]

..do a search and be sure to use OEM sw.
What happens with the codes is they will clear themselves after so many no faults , so an intermittant problem like a set of sw contacts can show as a no codes and still be the fault.............depending on when you go checking.
If the asr comes up again , immediately code check

Gilly · #14 09-11-2006, 03:56 PM

Yes the car certainly IS throttle by wire. The throttle motor is the part the "wires" are controlling. Located on the intake manifold.
Gilly

Gilly · #15 09-11-2006, 04:10 PM

Oh btw yes there are numerous names for the part such as the throttle actuator being most common I think, also something in the parts literature referring to a "slide", and also references to E-Gas. Alway been the throttle motor to me, has a rather large electric motor that opens the throttle plate/butterfly.
Gilly