Could my 2005 ETA be faulty?

[Kashpar]

Hello guys, need some help with my recently acquired '93 500E.

The symptoms:
Car frequently goes into Limp-Home Mode. Most frequent LHM occurrence is right after starting the car up, and immediately moving the gear lever to Reverse. The car surges back wildly, I can feel the gas pedal moving by itself, and then the ASR light goes on and car immediately goes into LHM.
At times however, the car lets me pull away without problems and then goes into LHM in the middle of a drive.

Both the upper wiring harness and the ETA were replaced by previous owners. The ETA has build date 05/05.

I pulled the following codes with my analogue reader:
Pin 6 DTC 30 (CAN data bus to EA/CC/ISC interrupted)
Pin 7 DTC 3 (many options) and 14 (closed throttle position switch)

I then took the car to my acquaintance at official MB dealership, who was able to pull the following sub-codes on the Pin 7 DTC 3: #048 and #049, i.e. reference potentiometer and actual value potentiometer. Based on this, he claimed my ETA is faulty.

I'm obviously having a hard time accepting the fact that I need a new ETA, since I believed that buying a car with replaced ETA will save me the trouble and expense.

So my question to you: are the 048/049 codes a definitive proof that my ETA is dead? Given the strange symptoms (surging on reverse), could it be something else? Closed-throttle switch, neutral safety switch/safety contact switch?

Thanks.

 

[nocfn]

is throttle cable in good working order, adjusted properly and spring present? Also, how is the neutral safety switch? I am not certain what the problem may be but investigation of proper basics might be an ah - ha moment. I think you may find the answer here, you are on the right path. (may be a cause or a symptom but either way needs correcting based on codes) GSXR?

 

[gsxr]

I would replace closed throttle position switch (S29/3) first and see if that cures code #14, along with triple-checking that all the linkages are adjusted correctly.

If you do that and STILL get codes 048 / 049, it's possible the ETA is bad. Not likely, but possible. The NSS would trigger a different code. I doubt the E-GAS module would be at fault.

Do you know how many miles are on the 2005 ETA? Also, have you physically seen the date code on the ETA and confirmed it was brand new in 2005? If it was just 'rebuilt' in 2005... or replaced with a used ETA in 2005... it's far more likely to be defective. Have to look at the label to know for sure.

 

[Matin]

I'm having extremely similar symptoms as you however my car does not go into LHM, but the gas pedal accelerates itself.

the only things that I have not changed are:

ETA (I have a spare one on the shelf but just been lazy to fit it)
Fuel pumps

my fuel pumps are buzzing so I'm going to change them this weekend to see if the problem goes away.

my ETA has a date of 2012 also..

 

[Kashpar]

Many thanks for quick responses.

Attached is the snapshot of the ETA date code. The car is a Japan re-import with only 72.000kms so if this was a brand new part, it can't have too many miles on it. The previous owner might have bought this ETA already used but I have no way of finding out.

I will try replacing the closed throttle position switch, check the linkage adjustments and report back. Thanks again.

 

[Kashpar]

So, finally had time to replace the S29/3 switch , which did cure the code 14 on pin 3. I also checked/adjusted all the throttle linkages and cables, no apparent problems there. However, the LHM mode is still very much present. I think I'll bite the bullet and order a brand new ETA...

 

[samiam44]

Just a thought before dropping a large amount of cash. Can you try a different E-Gas module? They seem to be the least reliable of all the modules- possibly the owner went too long and the shorting harness damaged the computer module.


Michael

 

[Kashpar]

OK, short update:

I bought and installed brand new ETA from MB dealer ($1.750, ouch!). This has cleared codes 048 and 048 on Pin 7-DTC 3. However, the LHM has returned soon after.
The reader again gives me code 14 on pin 3 - S29/3 switch, which I have replaced with new part a month ago. The LHM appears randomly, sometimes twice during one short trip, sometimes I drive around for a week without any problems. Restarting the engine always helps.

Any ideas why the S29/3 switch throws a code, randomly and without rhyme or reason?

 

[gsxr]

I assume you mean code 14 on pin 7 (not pin 3), but that is odd since you have a new S29/3 switch installed.

First - make sure the throttle linkage is adjusted correctly, per FSM procedure! With the new ETA, it may require adjustment. If it is not adjusted perfectly, it can trigger analog code 14 (digital code 224) on pin 7 (E-GAS module), because the ETA closed throttle switch (M16/1s2) is not closing at the same time as the closed throttle switch at the accelerator pedal (S29/3). The computers expect these two switches to close at the same time.

If you are absolutely certain the linkages are adjusted correctly: Have you checked codes on all other modules, including ABS/ASR module pin 6? Is there any chance the switch S29/3 was not installed properly, and/or there is a wiring problem somewhere between the switch and the module? Might want to check the pins and sockets under the E-GAS module. If all else fails, I'd try a different E-GAS module next and see if the same code keeps recurring.

My $$$ is on ETA linkage adjustment...

 

[nocfn]

Is there a How To and linkage adjustment?

 

[Kashpar]

gsxr, as always thanks for taking the time to help.

For linkage adjustment, I have followed the FSM procedure as outlined here:
http://www.w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Engine/119/30-1010EA.pdf
Admittedly, I'm a noob but I *think* I got it adjusted right. The tips at the bell crank/lever are opposite each other (within 1mm), the bowden cable has a tiny amount of slack, the bell crank is resting against closed throttle stop of the ETA, etc.

In terms of the S29/3 switch: the little black rectangular box that goes underneath the gas pedal is held in place by a small screw. When installing the new part, the screw wouldn't for some reason go in more than a third of the way. Could that be a problem? I had to leave it partially screwed in, but I did make sure to jam the box into its place underneath the pedal very tight, so I think there's zero possibility of it coming loose.

I don't get any codes on pin 6, besides the obvious #30. As for the E-GAS module, I don't have access to a different one, so can't experiment there.

If it's of any help, one thing I noticed is that when the LHM occurs, the car idles a little bit higher (about 1.200rpm).

 

[Jlaa]

Hello Kashpar, did you ever find out the solution to your problem? Thanks.