ABS Mystery

Any shop with the proper diagnostic tool should be able to tell you what is wrong with the ABS system. After any work is done on an ABS system the vehicle usually has to be driven for a short distance before it will reset itself. Just disconnecting the battery will not do it. The ABS system needs to recognize the signals from each sensor.

I had new rotors, calipers and pads put on my car, got an ABS light after, would come on and then go out. It took about a week of driving it and it finally stayed out

I read some of that in the book. It said to drive over 10mph. What I am still scratching me head over is how ABS worked at all before because there was no tone ring at all on the rear rotors. It's almost as if the system was disabled and light turned off in software or something. Ford parts shows the rears are supposed to have ABS rings but not the front. Front has sensors too. When I removed the old rotors, ABS ring was only present on front and not rear. I am replacing the rotors with no rings so at least I know all the mechanical components are where they are supposed to be when I get the codes scanned.

Your ABS sensors all have an electrical plug about 2' away. Take your ohmmeter and check the resistance of each sensor. ON my coach they all read about 1200 ohms. If all of your sensors have the same reading, then I would suspect that your missing ABS rings MIGHT be the problem, assuming that the main ABS module is working properly.
MY ABS sensors all read about 1200 ohms. Your's may have a different reading. What you are looking for is for all of them to read very close to the same.

delete

My guess is the prior owner rigged the system somehow and you have the wrong rotors for the chassis model. I'm guessing your chassis is a 20.5K lbs which was a four channel system and 10 bolt hubs. My lighter chassis, 18.5K lbs is three channel and 10 bolt. Since both have 10 bolt wheel hubs and disks that are interchangeable.

How the system could be rigged not to fault without the ring I'm not sure since the system is looking for a train of pulses as the wheel rotates? I have no idea. Anything passive such as an open, short, a diode or resistor wouldn't do it.

With ABS


Without ABS

Dale.Traveling wrote:
My guess is the prior owner rigged the system somehow and you have the wrong rotors for the chassis model. I'm guessing your chassis is a 20.5K lbs which was a four channel system and 10 bolt hubs. My lighter chassis, 18.5K lbs is three channel and 10 bolt. Since both have 10 bolt wheel hubs and disks that are interchangeable.

How the system could be rigged not to fault without the ring I'm not sure since the system is looking for a train of pulses as the wheel rotates? I have no idea. Anything passive such as an open, short, a diode or resistor wouldn't do it.

With ABS


Without ABS

22k chassis. I don't know either how the light was NOT on prior to me doing the brake job.
The actual part BRRF-234 that was on the front and SHOULD be on the front AND back. On the Ford site for parts, they claim BRRF-234 is only for rear.

This part, BRRF-78 was on the back and is still there now because I didn't know anything about ABS. On the Ford site, they claim BRRF-78 is for the front.

Ford parts site is all messed up. FYI in case someone decides to do this job with similar chassis weight/year.

No codes found. Cleared the fault (light off) and took a test drive. 1.5 miles the light comes back on, no codes again. Did this twice. New rotors coming in will put them on. Stealership won't look at it anyway unless all the mechanical stuff is correct.

All sensors tested good today. Found air gap on these is pretty large but spun front tire around while measuring and it did generate some voltage so good sign there. Tore down the rear end again. New rotors coming tomorrow.