2006 GP. 97K. Can't connect to ECU. Alternator changed in Oct-2018 with a BOSCH unit.

Using my OBDII scanner I can connect to ECU2 module as well as to the ABS, steering angle, and power steering, just not the ECU module.

I found an alternator load %. New battery installed before all this happened and I am getting 14.33/14.32 volts using a multimeter on the battery.

Is this normal for the alternator load to be all over the place?

Short video.


I confirmed continuity between the ecu connector pin 37 and pin 8 of the OBD port using a breakbout box and a multimeter via the purple wire with the white stripe. Also got continuity to the power steering pump connector and the cylindrical connector near the driver headlight as well as straight to the interior. I can see the DME2 (Digital Motor Electronics 2), ABS/ACS/DSC (Dynamic Stability Control), LEW (Steering-angle sensor) as well as the EHPS (electronically assisted power steering). But I cannot see DME. If there was a short to ground, it would take down the entire D-bus line. If there was a broken wire to the ECU/DME, it would not show continuity on pin 37 all the way inside to the OBD port.

So I'm thinking either I have a bad ECU or perhaps I have a wonky alternator that is causing havoc on the electrical system.

I also though maybe the power steering pump had something to do with it as the lines were leaking but I removed it from the car (as I was going to replace the lines anyways) and disconnect the plug as well as the direct connection to battery pos/neg and no change, still can't connect to DME.

The thing that is driving me absolutely bonkers is that this is happening to my WIFE'S 2006 MCS as well which has <70K. Her battery needed to be replaced too. Her alternator was replaced in mid 2016. I just can't imagine that TWO ecu's would go bad....but what I *can* imagine is two alternators that are 6 and 8 years old going bad. I read the avg lifespan can be about 7 years on an alternator.

This was the video here that helped me troubleshoot but in his situation that short to ground did indeed take out the entire dbus line.


Any help is greatly appreciated. I love these cars and want to drive them forever.

I'm going to ask my friend to come over and connect my scanner and see what the alternator load percentage shows on his 2005 MCS. He also has a GP. I tried connecting to my Tacoma and the Cadillac but neither one had that field available.

 

Given that there’s only one DME, my guess would be that it’s just mislabeled in your scan tool. Some BMWs have two DMEs - one per bank.

Pretty sure the alternator load signal is read by the DME, which indicates to me that you’re connected just fine. It sounds like it’s charging fine. I don’t know what the load percentage would normally look like at idle though. How’s idle stability? Is there an actual issue you’re trying to hunt down?