Well I wanted to jump in here for a little advice on my 931.
When I first got my truck, the ABS light was on. Just checking around, I noticed the ABS light connectors unplugged under the dash. Plugged them back in, presto, the truck checks the ABS and it's happy after that. I had driven it around for a bit without any issues.
Yesterday I picked up my M871 trailer. On the way home we noticed the right rear hub and drum being very hot. Also from time to time it felt as though the brakes were holding. Then it would suddenly be ok. The ABS light remains off though (after a normal start/check).
I was planning on pulling the axle tomorrow to check the bearings. (And I'm thinking about ditching the outer seal to make it a wet bearing instead)
So my thoughts are this. Is this indicative that there is a ABS issue on the truck? Seems like disconnecting the ABS warning light might have been intentional. I realize that the brakes might need an adjustment as well. The driver's side rear axle was a little warm as well.
It's my understanding from what I've read that the ABS system only actuates the rear most axle. Also I believe I recalled a blurb about the parking brake also actuates the rear axle parking brake?