'94 E320T S124 M104 - Won't Idle, Unknown Code

[RobertFini]

Hi, All.

I'm having problems with my '94 E320 tourenwagen; here's the lowdown:

The car was running perfectly, but had a starter problem that turned out to be the neutral safety switch. I don't have facilities to get under the car for that kind of work (plus I'm getting too old for it), so I had a local indie take care of it. Once again, the car was running perfectly.

Several days later, I go out to take a ride, start the car, she starts and runs for a second or two and then goes completely dead, with no lights on the dashboard. I try to restart, and get absolutely nothing: no clicks, no lights, nothing. So I lift the hood and see that the the indie was careless and hadn't properly tightened the negative lead at the battery terminal, as it's laying there loose. I put everything back to normal, the car starts right up and runs strong like she always has, pulling like a freight train all the way to redline and shifting clean, but won't idle.

Idle speed is around 400-500 RPM when she does idle, but surges, stumbles and stalls whenever I come completely off throttle. I swapped the OVP from my other '94 E320T parts car and it made no difference. Using my trusty Dalton code reader, I cleared the codes and drove around a bit, and the only two that came back are 47 and 49 on pin 8. Engine wiring harness has been replaced, no blown fuses in the underhood fuse box, 234k miles.

Code 49 is "Voltage supply at engine control module implausible/low volts" but none of the listings I'm able to find show a code 47 for pin 8, so I'm hoping y'all can give me some guidance on that as well as anything else to check.

Best Regards,
Rob