W124 E320 DTC and ETA issues
 

Ok, I picked up a '95 W124 E320 with the M104. Both the ABS and ASR lights were on, and the HG was leaking. (Yeah, I know, I'm a sucker for a project). The car actually drove great and the ETA was working fine (throttle was totally normal), but the ABS and ASR were both obviously non-functional...both tire spinning and lockup under braking were easy to achieve. I put almost 1000 miles on the car in this condition, and other than blowing a quart of oil out the HG every 150 miles, it was fine.

The main engine harness is in good shape, obviously replaced.

I checked and cleared the codes before starting the HG project:

16-pin connector, using the home-brew code reader.

Before work:
Pin 8 - DTC code 42 - CAN bus to EA

While I had the HG off, I cut open the sheathing on the ETA harness cable. The insulation was GONE. I mean COMPLETELY degraded (and this car supposedly had the ETA replaced at the dealer at about 50k miles!). So, I attempted to rebuild the ETA wiring harness according to the online write-up. Maybe I got it right, and maybe I didn't...

After work:
Pin 14 - DTC code 3 - ETA
Pin 8 - DTC code 8 - Limp-home, 42 - CAN bus to EA

Now, after the work, the ETA does open and close during the self-test at ignition on. And going through that self-test does not throw the DTC code 3. It will only throw that code after running the car. And clearly the ETA is not functional...LHM is present and the car is virtually undriveable.

I did do the throttle linkage adjustments, and removed-installed the ETA a couple times checking for the obvious problems, with consistent results above.

2 questions now:

1 - I'm tempted to try the BBA rebuild service for $400. If they try to fix it and can't get a good bench test they tell me I'm only out the shipping charges. Is this a good idea?

2 - How do I test the CAN bus? I had hoped that repairing the ETA wiring would help this, but obviously I made things worse. Should I test something to ensure that the CAN bus problem isn't causing additional issues?

Any thoughts are appreciated!

Did you check the OVP relay / cure the ABS & ASR lights?

I did replace the OVP relay before the HG project. No change to the ABS & ASR lights. Thanks, I forgot to mention that.

No other thoughts on this? If not I'm going to go ahead and send the ETA to BBA today, hopefully they'll have more luck with it than I did.

How about all the other components related to the ABS/ASR?
Brake Switch, Neutral Safety switch. They are cheap and easy to replace.

There are two other companies that rebuild ETA's, they are Beckmann Technologies, and 4Mercedes. BT is a little more expensive, but they were very very helpful when I dealt with my ETA problem. 4Mercedes would probably be OK as well, but they were less helpful when I talked to them on the phone. There are three common ways these things fail. They are bad wire harness, bad motor, and bad feedback potentiometer. Bad wire harness is DIYable if you are handy with a solder iron, and have some craftsmanship skills to disassemble/reassemble the plug. A bad motor can not be fixed as the motor is a press fit into the housing. BT is the only rebuilder (at least to my knowledge) that can repair a defective feedback pot.

Many DIY rewires have failed because of a bad motor or pot..... (my record is 50/50)

If I were to have this problem again, I would use BT even if they cost a bit more.

J. M. van Swaay

Thanks for the feedback, guys. Since the car was driving OK (not in LHM) before the HG and harness rebuild, doesn't that mean that the motor and feedback pot in the unit are working ok? (it still looks like the power on self-test is working, so I believe the motor is still ok regardless.)

Did you actually peel back several inches of the black fabric wrap around the engine wire harness when verifying its integrity? At first, mine looked good, but closer inspection revealed major insulation decay....

Maybe you read this already--it details my ETA experience. Maybe there is some beneficial info.

http://www.peachparts.com/shopforum/showthread.php?t=164083

Good Luck

Yep, I did read that thread, thanks. Good info there, I'm pretty sure I hit every ASR/ETA thread on the board over the last few weeks! Forgot to mention that I also rebuild that same 'starter lockout' 3-wire harness that you did in your thread, though I doubt it is related.

I peeled back an inch or two in a couple places on the harness and am pretty comfortable that it is good. It's in beautiful shape compared to the very obvious failure of any of the other 'original' wiring in the area (starter harness, ETA harness)

Update: I did purchase a rebuilt unit from Beckmann ( http://www.beckmanntechnologies.com ). They have an exchange program for $760. BBA was $400 for the exchange, but after speaking with Andrew at Beckmann I felt very good about their knowledge, level of service, and competency. Nothing against BBA, I was just impressed with Beckmann and appreciated J.M.'s experience as well.

I was happy with the experience and the part arrived in good order and worked on the first try. I have good ETA operation again, the car is very driveable and I'm back to code 42 on pin 8 as before.

So, I still have the ABS/ASR lights on, and no ABS/ASR functionality, but the car runs and drives very well so I can keep troubleshooting while I use it.

I replaced the brake switch as well, to no effect.

Do the lights come on immediately after start up, or once you start driving?

It still sounds like a bad harness...

Lights come on immediately. Even after clearing the codes, there is never a time that the lights are not illuminated...they come on during the test with the ignition key and stay on when the rest of the lights extinguish.

I still would like to know how I can test the 'CAN bus to the EA module'. I've tried looking in the WIS for some kind of pinout diagram of the connector and haven't come up with anything.

CC work??

No, CC does not work.

I know you have probably done this 1000+ times, but I would check all the connections behind the battery box. Perhaps something came loose while replacing the OVP. Disconnect them and reconnect them. I also wouldnt rule out the possibility of another faulty OVP. Is the fuse ok on it?

Both lights on constant before speed indicate no power...OVP fuse is first suspect, fuse #7 is second.

Do you have 12V + at pin 16 of DM to ground?

Well, per the recommendations here I went back and investigated all the connections behind the battery. Part of the connector to the OBC had been disconnected and tucked away down under part of the battery tray. This car was diagnosed as having a bad OVP relay by a local shop with a bad reputation before I bought it...I suspect they disconnected it deliberately and were hoping to get the replacement cost out of the previous owner.

I didn't catch it when replacing the OVP because I didn't dig deep enough and didn't know these cars well enough to know how that connector works....though I thought it was weird that 3 of the pins from the relay weren't connected to anything!

So, now my ASR/ABS is working great, car is running well. Thanks!!

I love happy endings...

That was some great inexpensive advice!