Trying to scan ABS codes on 99 Dakota with Snap-on scanner

Well, there's no body control module on a Dak, so that's out. And as far as I know, the ABS system is dealer-proprietary - only a DRBIII can talk to it (every independent shop I've talked to has always said 'dealer-only' when it came to anything to do with the ABS system)

IIRC, the manual for my RAM said that you need to use a breakout box and jumper a few pins to communicate with the antilock brake controller.

I know that was the case with the '94-'97's... I don't know if it carried over to the newer ABS systems. In fact, now that I think about it, a buddy's '98 1500 with 4W ABS had a problem... he took it to several places, and they all told him the same thing: "dealer only - nothing we can do". We did what we could, troubleshooting the wheel sensors (all checked out good), the brake switch, bled out what we could, etc. Never could determine the problem - so he sold it :)

Well, the output shaft sensor seems to be working according to the scanner. Funny thing is that the speedometer jumps around alot under 25 or so mph. On the lift with the truck in gear the speedo doesn't move until after 20-25 mph even though the output shaft sensor reading varies directly with observed shaft movement. I'm thinking rear wheel sensor. There is only one and it is mounted on top of the rear end pumpkin.

Aw, heck - if you would have said that to begin with... :) Yeah, classic symptoms of a failed rear wheel speed sensor. Speedometer reading comes from this sensor (via the ABS controller) - not the trans output sensor. ABS+brake lights+funky speedometer == bad RWSS.

Thanks Tom!