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formerly W6FZC

My Mercedes Benz
S500 Coupe

K6JRF's MB S500 Cpe
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(Updated: Mar 9, 2018)

Yet another ASR problem!

ETA Video Repair Update (3/9/18) . .

Before wading into the details of ETA diagnostics, I recommend that you take the time to look at Victor Sevryugin's web site here. It may change your mind about repairing your ETA!

His web site contains a wealth of Mercedes repair information including ETA repair employing a video "primer" course on the art of ETA repair.

This link shows how to detect a going/gone bad ETA and how to inspect the ETA wiring harness to confirm that it's bad. This video is for a '95 SL500.

Victor will repair or rewire the ETA complete with harness for a very reasonable price if you want. He also can repair / rebuild most other parts such as the engine wiring harness, closing assist pump and most other systems in the car.

All I can say is, I wish I lived in Brooklyn!!

Mercedes Shop Forum is now PeachParts Mercedes Shop Forum


ASR stands for "Acceleration Slip Regulation" and it is Mercedes way of guarantying that the wheels have equal traction when you need to accelerate quickly.  But the ASR system is tied to all of the electronic systems (EA and LH-SFI) in the car, so everything needs to be working otherwise the car is forced into the "limp-home" mode (LH).


Recently, my car developed this problem and this thread is documented as it happened in a daily time format.


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


The ASR problem seems to occur in two distinct ways:  It can occur while driving and gives the driver quite a start! The car goes into the LH mode (will be described later) and the accelerator pedal does not respond as before.  It’s quite a ‘trip’ to drive the car.

The other way is the ASR MIL lights when the car is started. Again the accelerator pedal does not respond (forced into the LH mode) as it does normally and the car is quite a chore to drive!


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 restart. 


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



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 re-cycling the ignition.

4)    It NEVER comes on while driving.



Yesterday I dumped the DTCs using an AST Retriever Scanner:

Base Module:  No codes

Diag Module:  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.


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 re installing 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.



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. Recheck the codes and they are still the same as reported previously.

Well, 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.  That probably was 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.


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'.

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.


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!

Here's a overview drawing contributed by a MSF member, Russ McMahon. It shows the details of the parts that need to be removed to get the old ETA off and new one installed. The detailed removal and installation instructions are below the main picture.

Diagram of M119 engine ETA Removal and Installation Instructions

Attached a picture of the 'beast': it's some kind of assembly!





















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: i.e., after using an AST scanner to reset the codes and recycle ignition key, the codes would immediately reappear 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???

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.

This is 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 forward to disassembly the part to see how it's constructed.


Update: 9/23/03  . . .  

My car appears to be fixed!!

A KEY troubleshooting fact: When reading DTCs from the EA/CC/ISC module hooked to a properly functioning ETA, a mechanical sound will be heard as the motor turns and 'resets' it's position. It can clearly be heard. Needless to say, that sound was missing from my car with the old ETA. Another 'clue' that points to the ETA assy. Check out Victor's test of a repaired ETA here on his SL500 showing that the ETA should "buzz" if it's ok. That's the clutch engaging. You can statically test the repaired ETA by substituting it as shown in the video. This will assure that the repaired ETA will work when installed.

Got a chance to take the unit apart and see what this electro-mechanical monster is all about. The pictures show the as-opened condition: there was no dirt, dust, etc. Nothing 'smelled' burned.

The first picture shows the 'business' side of the unit with the motor driving the butterfly with the clutch coil that provides the linkage to the butterfly assy.
























This picture shows the reference potentiometer board where the metal pickup slides over the resistance material as the butterfly is opened and closed.
























Schematic diagram of M119 ETA

Connector Detail Diagram

But I haven't taken that apart yet. May have a better picture when I do. The schematic diagram is for a '94 M119 ETA. Thanks to Mike from the Mercedes Shop Forum, here's a schematic of the ETA, clearly showing the major components in the unit: m1, motor; r1, reference potentiometer and the interface pins on connector, X1.

Would be nice to . . .

be able to refurbish the unit since they are so expensive. Retail price at a MB dealer is $1000 plus tax; wholesale around $750. Personally I got a great price on a new one because of 'payback' time!

I contacted VDO and waiting for a reply. Trying to find a qualified repair center. But I have a feeling that a repair facility for this part doesn't exist.

Speedometers can be repaired/refurbished but I don't think that these units can be unless they go back to the factory in Germany. The main problem appears that the Reference Potentiometer (Ref Pot), key to proper operation of the ETA, gets severely worn and is the 'weak link' in this Mercedes part. Unless the Ref Pot can be replaced with a NEW one or remanufactured using specialized equipment, repair would be fruitless.

Update: Jul 14, 2005. . . .

Recently along this line, I asked Robert Beckmann of Beckmann Technologies (now known as BlueLink Diagnostic Solutions) about repair of an ETA, specifically the Ref Pot. Here is his reply with my questions as framework.

[Is it a key part in the repair of an ETA?] Yes, that is true.
[Can it be repaired? Do you replace them or rebuild them?] We have developed ways to restore the pots in most of the units. Some are so bad that they get tossed. Perhaps 10% or so. The specifics are somewhat of a trade secret and not something the DIY folks will want to tackle since it requires some specialized equipment. Also very important is the alignment and testing of the actuators. We have a pretty comprehensive test fixture which allows us to run them on the bench in full servo control mode. This has really made this an excellent product for us. We are certainly much more expensive than the others but still very competitive when compared to the factory new parts.

Not to ramble but some years back we found it in our best interest to dig deep into the diagnostic aspects of the later control units. This allowed us to test/repair many of them with great success. This also included ways to unlock the units (1996 and later) which allowed them to be installed into other vehicles and reused. This has been good for us since I believe that aside from Bosch and some dark closets at MB we are the only company which is able to do this.


Updated Comments (1/23/05). . . .

Recently, I was informed that BlueLink Diagnostic Solutions (formerly known as Beckmann Technologies) now rebuilds the unit. Not sure the cost involved but contact them at 919.226.1377

Email from a Beckmann customer: "Beckmann rebuilt a unit for me and it has worked for the past 5 months on my '95 SL500." Name withheld by request.

Received another email stating that Automotive Scientific Inc also rebuilds the unit. However, the ETA did not work at all. Here's a summary from the person who dealt with them.
"I spent 6 months trying to get an ETA that wasn't DOA. Never got a working ETA from them and wasted $675.00 plus shipping both ways on 4 occasions. They wear you down taking the unit on and off the car and shipping it back until you give up. The ETA from them was 'checked' and I was told that it was junk!" Name withheld by request.

The following updates show that you CAN repair the ETA if you are willing to dig in and can follow a schematic and that the Ref Pot is not too worn. You do need some good soldering skills and need to check, check and then recheck everything. So if the ETA has failed due to bad wiring only, then it can be repaired. However, if some of the internal components such as the Ref Pot has failed, you will be better served by purchasing a new unit even though it is expensive. You can NOT fix a bad Ref Pot since once the resistive material "wears", it can not be 'fixed' unless you have a specialized microelectronic facilities that can deposit 'resistive' material. So you will not be able to successfully repair the ETA even if you rewire it perfectly! Unfortunately, there are no suppliers for a replacement Ref Pot.

Link to Mercedes Shop Forum (4/28/05). . . .

One of the 'ambitious' members has decided to rebuild his ETA and this link is to the post showing the progress to date. Suggest that you follow this thread since it contains detailed pictures showing the deteriorated wiring inside the ETA. This appears to be one of the MAIN source for ETA failure as the pictures show. However, upon re-assembly and installation into the car, the car did not operate properly . . . probably b/c the ETA was not disassembled to see what OTHER parts, beside the wiring, had failed. Please note that the 'ETA' is referred to as the 'EA', so you will need to do some mental translation. [Update: unfortunately, the link is dead]

Link to '95 S600 ETA Repair (4/24/05) . . . .

Another member of the Mercedes Shop Forum decided to repair one of the two (2) ETAs himself and this link takes you to his web page. Good pictures and details of the internal wire repair and how-to-repair the mating connector as well as the complete Electronic Throttle Actuator. Unfortunately, the link is no longer active!

95 S430 ETA Repair (6/10/05) . . . .

Today I met 'normwm' from the Mercedes Shop Forum at my tech's shop. His 'home-brew' repair of the ETA did not work as expected; the ASR light comes on immediately and it goes into LH mode. After reading the codes, the DM#6 DTC . 'ISC faulty' was still showing and wouldn't reset. So here's another instance of the some internal part (clutch, Ref pot, etc) causing a non-repair of an otherwise well done rewiring of the unit.

95 C280 ETA Repair (12/1/05) . . . .

A new company was brought to my attention today. They repair many major electrical and electro-mechanical parts for Mercedes. They specifically mention, 'speedometers', 'instrument clusters', 'throttle body actuators', 'vacuum pumps', 'power top control units' and 'amplifiers'. These are major cost items on all Mercedes. The company is called 4Mercedes.com from Pompano Beach, FL.

Please note that "4Mercedes.com" link is dead. However, there is a "4-Mercedes.com" that is located in Oakland Park, FL. Not sure that the two are related . . . but I'd be careful!!
I've received a report about "4Mercedes" that needs to be posted so both sides are presented. "Thomas" from Brunei tried to get his EZL unit repaired. Here are his words:
"How to contact the company manager, i did send the item to him, and he "4mercedes" send me a invoice and i pay, after that the item never send it back to me, i try to call and the phone is on the answering mode and never return call, i try to call my friend in us to help to call that company and same problem, until now i loss my money USD 2K. if you know any one in the company pls let me know".
If you do business, be careful . . .
I received another email about "4Mercedes" that also needs to be posted. "Elmer Mack" tried to get his ETAs repaired on his '94 SL600. Here are his words:
"Having problems with my 1994 sl600 with the ASR, I referred to your website and thought that I had investigated 4Mercedes of Pompano Beach, Florida enough to trust them with the repairs/rebuilding of my ETA's.------Bad---Bad Choice.

To begin, they quoted $6,500 to replace both ETA's and a complete engine wiring harness........Once I shipped my car there from Baltimore, the scenario changed very quickly as they were now only willing to replace one (1) sub wiring harness of this multi-wire engine harness.......This did not correct my problem.

I received my car back, two months later and the ASR light came on instantly with the car going into the 'limp-home' mode...... To hide their poor repairs here, they opened the Instrument Cluster and just simply removed the light bulb from the dash mounted 'Check Engine' light feature.....Documentation from a noted M/B dealer, before shipment verifies that this 'Check Engine' was fully operational and staying 'ON".....indicating an engine failure, and that the light was in place and operating properly.

I had trouble getting 4Mercedes to release this car for transporting back to me.........Why ???...because they were using it for their private grocery cart. They put an incredible 765 miles on it while it was at their facility......My driver side car seat was now totally inoperable with an unopened box of kids cereal jammed up underneath the seat. ...Worse yet, under the hood they had not installed the wiring harness for the ETA in the proper place and the rough edges of the computer box surround where now cutting into and chaffing these new wires......Also, the computer box surround cover was not secured back in place with any type of fasteners. The top for this computer box surround could not be secured back in place because someone had left a screw driver underneath it.

As well, the rear storage compartments where stuffed with old newspapers. Now onto the worst part, 4Mercedes, placed this billing on my credit charge with an unknown third party who is disclaiming any responsibility for this poor service repair work.... Obviously 4Mercedes has not responded with having someone look at my car, as he has promised. Today is being investigated be the local Sheriffs Office for credit card fraud......My credit card company, Bank of America, refuses to make an adjustment under the rules of their Billing Dispute with the statement that the Invoice from 4Mercedes was not broken down enough for them to make a finding of incompetent workmanship, and that my claim for reimbursement does not lie with 4Mercedes but with the unknown third party who placed this billing with Bank America.... JUST CRAZY!! I WOULD WARN EVERYONE TO STAY AWAY FROM 4MERCEDES AND MARCO KOOP.

Another Source for ETAs (9/27/07) . . . .

A new company was brought to my attention today called Jaytan [web page is not active] located in Orange, CA. Their prices for rebuilt ETAs include a 'core' charge which is refunded when the 'core' is returned. Prices are reasonable and have a two (2) year warranty.

Since their "product" prices looked reasonable, I recommended that we give them a try. Pat currently had a '92 SL500 in his repair shop that was badly in need of a new Fuel Distributor (FD). The one on the car was partially plugged in one port and that caused a steady miss in the engine. So Pat purchased one and it was promptly received. So far all is good!

After installing it, that FD turned out to be worse than the original unit so it was removed, returned and a request for another unit was made. After a few phone calls from yours truly, they did send a replacement unit, albeit three weeks late. This one too was as bad as the first unit so it was returned.

Another two weeks elapsed and still no replacement fuel distributor. A few phone calls were made that resulted in a "new" unit. This one worked perfectly and so the saga is at an end. Other than prompt replacement of the third defective unit via UPS Overnight shipping at Jaytan's expense, the results using their rebuilt products are still yet to be determined!

Replace the ETA Flying Cable (10/28//07) . .

For those who decide to rebuild the ETA, this is good data. The old style plug (90 deg bend) with the cable is available separately from Germany very cheaply. If you have the needed soldering and de-soldering skills, you can replace the cable and hope that the internal parts are OK! The PN is 140 540 15 81. Mike ("myamar" from MSF) ordered some a few years ago from the site's owner, R&R Import Parts Roy Tucker.

Another Source for MB Parts Rebuild (5/7/08) . .

Learned of another company, BBA-reman that rebuilds various MB parts not the least of which, is the ETA. Prices are very reasonable and come with a 2 to 3 year warranty. Part turnaround is 2 to 3 days. In many cases, they have a 'replacement' part that is sent to you immediately and then you return the 'core'. If you don't, an extra charge is incurred. Prices for a ETA rebuild are apx $432.

I received this email (9/26/08) from "Brian" re his ETA repair using BBA-reman.
I sent the ETA (000 141 79 25) from my 400E to BBA-Reman for repair. They returned it within a week as repaired. They replaced the cord, which I had already split and looked inside and need replacing. It was in surprisingly good condition. I determined the problem was internal to the ETA after scanning for DTC's.

When I installed the repaired unit it was almost as bad as when it went to them. Returned it for repair under warranty. Waited over a week and received a "replacement" ETA with the explanation they couldn't repair my original one which begs the question "why did you send it back as repaired in the first place"? Smells fishy to me!

The replacement unit came still with the factory harness, so I guess they decided it was OK. No idea what was replaced inside, if anything. It turned out to be the worst of all. Car wouldn't even idle. At least before it was driveable......until it got hot.

I have a Snap-On MT2500 scanner and it is giving me a code 050: "Safety Contact Switch M16 1S1" which is internal on the ETA.Don't know how their testing equipment missed that.

So, I'm out $400 (although I will ask for a refund, which doubt will be forthcoming) and still have a car that is undriveable with an ETA that is worse then the one I sent for repair. Sure does take all the fun outta DIY!

Of course others may have had a better experience, but I don't think BBA are really set-up to properly repair ETA's. Just thought you might like the update.

I received a follow-up email today (10/17/08) reporting the final outcome:
BBA did finally provide a refund. However, this did not include the 2 additional unneccesary return freight charges of $36 I incurred because their unit didn't work in the first (and second) place.

The unit BBA shipment looked like it came from a recycler. If they couldn't even clean the exterior to work on it what is the inside like? No surprise it (they) didn't work.

Beckmann Technologies provided a more expensive rebuilt ETA.....THAT WORKED....first time!!! The unit had been cleaned and packaged professionally. The extra $150 (after core refund) was well worth it.


Another Source of MB Parts (5/6/09) . .

Talked to John Hervey of "SpecialT Auto" today and got a chance to peruse his excellent web site. Talk about MB parts rebuilding, he may have the largest parts inventory around! He's been in this business a long time and has a lot of satisfied customers.

Click here to see the large inventory of rebuilt MB parts. You can call him at 888 278-1629 to arrange a 'swap' of you needed part. He cautioned me that the "old" part be intact so that he can either rebuild it (if there's no stock for your part) or send you a replacement from his inventory. Without a "core", the minimum core charge could be excessive based on the number of "core" parts he has.

Update: ASR Revisited (10/19/07) . . . .

About 6 months ago, my ASR light came on when the car was started after driving. Turn off, and restart it and all was normal. From then on, intermittently, the ASR light would 'flash' but not stay on. When I read the DTCs, here's what showed.
1) DM, Code 6: ISC faulty    <--- this code showed "sometimes"
2) EA/CC/ISC, Code 7: EA ECU faulty or Starter Lockout-Backup Lamp Switch (S16/3) faulty

Sometimes the idle speed would 'seek'; idle at 625rpms then quickly climb to 850 - 900 rpms, then slowly come back to 625rpms. Typically it would go back and forth within this range. If I 'punched' the pedal (throttle), it might go into LH mode w/ the ASR light on. Again re starting the car, all would be normal.

I had the old VDO ETA repaired by Beckmann about 9 - 10 months ago just to see what went bad and to have a backup ETA "just-in-case"! Thinking that it was the REF POT assy in the ETA, I was surprised to find it was OK. The wires were 'toast' (that was expected) but the main failure was the butterfly clutch coil had failed and was open-circuit. It consists of a coil of wire where dc current is passed through it to control the butterfly valve action. Mine just 'died' from old age! They rewired and replaced the coil along w/ the crumbled wires. When it was returned, it sat in a box in my garage. I was already to replace the ETA (only 4-1/2 yrs old) if the present events got too bad.

Neutral Safety Switch (S16/3) The problem never got any worse and it was intermittent; normally when the car was cold, there was no problem. Note the similarity to the first symptoms described above. When I purchased a Palm Scanner (got great deal on a almost new one), I was able to read the DTCs as soon as an "incident" occurred. Sometimes the DM, code 6 (ISC faulty) wouldn't be there but the EA code, code 7 (EA, N4/1 or S16/3) was always present. Lately, I could not erase the EA's two DTCs meaning that the codes were currently "active". From Menu#9, the EA requires the S16/3 switch for ISC, brake info and selector position information, so if it's intermittent, it very well could be that switch!

Today, my tech had some time so he replaced S16/3 [000 545 62 06] switch (also called the Neutral Safety Switch) [NSS] located on the side of the transmission. Switch cost $65.  Well, I'm happy to say that was it!!!

Find out what failed . .

NSW - top Opened the NSS to see what was wrong and the pics show all! Nothing was broken and other than being 13 years old, it was mostly just worn out. The main problem is that the dual-lever switch contacts are ohmic and/or not making contact b/c of the worn "tip" on the selector lever. The back and forth movement has worn enough off the tip so that the switch doesn't make contact. All resistors were ok as were the solder joints.

NSW - bottom
So, bottom line, it's fixed again . . . until the next time!

Check back here to see any recent updates or additions to the ongoing ETA saga!