ABS light stays on?

Hi guys. I was reading this to learn the solution, and something came to mind. A few years ago I was following a similar problem, also on a Ford van. The owner claimed the brake pedal became impossible to push down, and if it was already pressed, it would push back up by itself. As I recall, this was an intermittent problem, and very dangerous. What reminded me of this was the fault code relating to an erratic rear signal. This other fellow's problem turned out to be metal debris that had collected on the tip of the rear sensor's magnet. By the description, it sounded like a bunch of little ears broken off the clutch plates for a locking differential. He or I may have interpreted that wrong. I do know it's not uncommon to find a coating of slimy fuzz on the sensor, meaning very fine metal filings in the gear lube and stuck to the magnet. Anything metal stuck to the magnet in that type of sensor will interfere with its ability to generate a signal the computer can read.

I have a couple of other thoughts you might consider. With the mechanics' disagreement on "electronic" vs. Something else, it sounds like they're referring to the type of anti-lock brake system. I've heard people refer to "rear-wheel-anti-lock", (RWAL) systems as hydraulic because they use a dump valve under the driver's seat, on the frame rail, and those only reduce brake fluid pressure to the two rear brakes. The brake pedal will gradually drop closer to the floor during that braking cycle, but only when the system activates. It only prevents rear-wheel lockup.

These same people will refer to "four-wheel-anti-lock" systems as "electronic" because there's a big hydraulic controller that often has a computer module bolted to it. In fact, both systems are electronically controlled, both use electrical sensors, and both modulate brake fluid pressure to a wheel that's slowing down too quickly. Your van will be of the four-wheel ABS system because it has sensors on the front wheels.

I don't know if this applies, but a possible reason no one wants to replace the rear sensor's connector is they haven't diagnosed the need themselves, and don't want to be blamed when it doesn't solve the problem. They also may fear you'll leave the shop confident the system will work if an emergency arises, and if it doesn't help prevent a crash, they may be party to a lawsuit. Mechanics have to have that in mind every time they touch a vehicle.

Most shops are also rather funny about installing parts a customer provides. That's like bringing your own food to a restaurant and asking them to cook it for you. If you don't like it, who is to blame? Sometimes, especially with old or rare cars, the shop may ask you to do research and find parts so they don't have to do that, but it should be made clear what happens if it's the wrong part, or it fails in the warranty period. When the shop procures the part, they mark it up a little to form a breakage fund. That fund pays the mechanic to do the job a second time if the part is defective. He did nothing wrong, so he deserves to be paid the second time. The car owner did nothing wrong, and he doesn't get charged to do the job a second time. Those benefits are lost or are in question when the customer provides the parts.

I would expect to be given a reason when someone refuses to do what is requested. That will give you an idea on what to do next. One last resort to consider is to visit a community college with an Automotive program and talk with one of the instructors. At my school, we were always looking for live work to give the kids real-world experience, and we had about a dozen community members who would sit on a broken vehicle until it matched what we were teaching. My "Electrical" class, for example, was only taught once a year, for eight weeks. The students have to learn how to solder and perform wiring repairs before we would bring this repair in, and it could only be during those eight weeks. To do electrical work outside of those eight weeks, such as in "Suspension and Alignment" class, would take away from our already too short time in that class, and it would take work away from the shop owners in our community who hire our graduates. At the very least, an instructor who isn't in class will gladly take the time to answer any questions, and possibly point you to a reputable shop that can help.

Hope this gives you guys some more ideas to pursue.

Okay, now that I know what you have for a scan tool. Select just the front sensors and the rear and switch them to graphing mode (the little hill looking thing on the right) now go drive on a rough road and then stop and look at the graphs. What you are looking for is drop outs in the signal, which is all that is needed to cause this. Then we can discover why. If there are no drop outs but the light is still on, then it could be the module itself not reading the signal internally.

Doc has some good points in there. I would second an automotive related school if you have one. Most do "routine" things throughout the class, but they do take tougher things later in the classes.

Yeah that doesn't look good, but we have another test that should tell you once and for all. It is a substitution test. You know the fronts are good and the rear is suspect. So, what we will do is "swap" the sensor inputs at the ABS Module. Basically, you know the sensors are sending data, but if you were to take the right front signal and send it to the rear input and it still showed the rear as the problem you know it's the module. Which can be found used,
To do that we would find the ABS module harness and swap the wires shown in the picture, either by cutting them or depinning. If you still see the same issue, then it's the module.
Now there is another option but I'm not going to tell you, but if you look in the location picture you might see something underlined. You had the brakes repaired and they work, while the light is on the ABS is off and it drives like a van without the optional ABS. If you can deal with that it's possible to turn off the ABS and the light in one step. Remove the optional ABS. I drove a lot of vehicles that way because I grew up on RWD and no ABS so many got the connector unplugged in my GMs.

Hissing is usually a sign of a vacuum leak in the booster, unless it is momentary. Like you step down and hold the pedal and it stops it's likely just a valving issue, if you step on the pedal and it hisses the entire time that's a leak. It sounds like the ABS is intermittent as well. If you were to pull fuse 19 in the under-hood fuse box it should deactivate it and let you see if it is the ABS causing the jerky stops.

Well, that relay isn't very secure any longer, I suspect they tried to remove it and damaged the case. That is the trailer running light relay. Removing fuse 19 would have disabled the ABS system (not the light but the ABS module and sensors). As that stopped the jerking and the hissing then it sounds like the ABS control module is the faulty part. With it partially operating it is trying to engage and disengage while you stop. Doing the sensor swap would pin it down but with your situation it may be a while before you can find a shop that can actually do the testing without just swapping out expensive pieces for you to pay for.
As such you can still drive it until you get it repaired but to turn off the light would require you to remove fuse 19 and Fuse 1. That should turn off the ABS system fully. It may not turn off the light, Ford did some strange wiring with it and used another fuse to power the light. If the brakes now work without the jerks and noise, then it is the ABS module itself that you would need to replace. You might try www. Car-part. Com to see if some yard near you has a used one, they could ship.
There is also the option of bulb removal to turn off that light if fuse one doesn't but that would be entirely your choice.

Yes, it's up front under the hood. That site should show you salvage yards to look at. It's a sort of watered down version of the Hollander interchange that the yards themselves use to look for parts.

No worry about the time, we will still be here.