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!