94 V6, 130k miles
ABS Inop warning lamp has been on since I bought the car 2 years ago. The PO says it was on when *he* bought the car in 2005 and he never did anything about it.
A scan showed a code for one of the hydraulic assembly motors having a fault. RF motor IIRC.
With a blown engine I had more important things to worry about than the ABS warning lamp. Since the car's been on the road, however, I've been systematically fixing the little problems. I held off on the ABS problem because I knew it would be messy. As in brake fluid messy.
This morning I swapped in a used hydraulic assembly from a junked 94. Of course I had no idea whether it was good or not. I resisted taking it apart to check it out because I knew I might screw something up inside it.
Well with the swap completed the ABS inop lamp is still on.
I figured I now had nothing to lose so I took apart the old unit. It wasn't hard at all and i don't think I broke anything. Lot's of stuff in there and not what I expected. Pics coming.

 

Here's the motor pack. 3 DC motors, apparently direct drive. All turn freely in one direction but seem to have a clutch that prevents rotation in the other direction. I thought I might find a seized one but that isn't the case. They're probably all good. I meant to hook them up to the wiring and turn the key to run and see what happened but kids were driving me nuts and I forgot. I'll do it shortly and report back.

 

Here's the main housing with solenoids and pressure rams/chambers. What's going on inside is a major mystery to me.
Obviously the electric motors' output gears drive the big gears seen here. What i find really odd, though, is that when you turn the big gears (very easy) you can go maybe 6 turns and then they stop solidly. I guess the internal parts (rams) might be hitting a stop after which they ratchet but I didn't really twist hard because I don't want to break anything.
You can then turn the gears the opposite direction for about 6 turns and then they stop again.
So the gears turn to move a ram up and down inside the main housing but how does that work when the electric motors only turn in one direction.
Anyone have experience with this system or have the AC-Delco training booklet? I'm sure that GM gave a class on this when it first came out.
Here's what the main housing looks like.

 

Update. I went to the car and hooked up the wiring harness to the old motor pack. When I had my son (3 1/2 - he's starting young) turn the key to run just 2 of the motor pulsed. The one for the RFbrake circuit did nothing. Tried 3 or 4 times and "helped" the motor once or twice. Nothing. So either the motor is bad or the circuit driving it (the EBCM) isn't working.

I'll get a schematic from a local shop and take a look at the wiring.

 

Okay, another update... Looked at a schematic and found out which connector pins are for each motor. I hooked up a cordless drill battery to each one of the motors and all worked. I even tried each with reversed polarity and they ran that way too so they *are* reversible. No speed or sound difference from any one of the motors. Looks like I have a bad EBCM. Bummer. It's back to the U-Pull-It for a spare or two. <sigh>

 

Oh, if you're interested in the ABS VI system read this:

http://findarticles.com/p/articles/m...g=content;col1

 

Good info. I have the same issue on the explorer we have but have not done anything with trying to trouble shoot it because the guy at the Ford dealership said the parts would cost more than the vehicle was worth.

 

Not sure about the GM but I did read somewhere on line that the computer has to be reprogrammed with the serial number of the new unit you are putting in or the ABS light would not go off. Did you see a serial number on anything?

 

I've had extensive expierence with this same issue. I don't my problem is the same as yours though. I ended up replacing everything in the ABS system, about $2500 worth of motor pack, ABS hydrollic unit, and ECM. I was getting the same code and every time I replaced the motor pack it just kept coming up with the same code. But you have to use a computer to bleed this cars and clear any ABS inop lights. My problem has since appeared to be somehow related to moisture. I had this problem for the last two years I lived in Florida right on the water, then I moved to Tucson, AZ and it went off on the drive out there and now only comes back on when it rains, and only every now and then. Still shows the same code, RF motor short to ground. I've checked all the wiring front start to finish dealing with the ABS and haven't found anything, no signs of corrosion. I hope you have better luck with you're ABS than I did.

 

That's what junkyards are for. The GM price for a new ABS controller is $1500, LOL. No, I don''t *think* so... I'll hit the U-Pull-It yard and buy one, two, or three of them for $20 each. One's gonna work. Too bad only a 94 part will work but with almost 120,000 built I should be able to find a few in yards.