I've been wrestling with my 2000 F-150 XLT 4WD ABS for a while and have learned a few things worth sharing.

I bought the truck with the ABS light on and am determined to fix it. The first problem discovered through this forum is that the positive (red) wire between the HCU pump and the ECU that mounts on top of the HCU gets corroded; more like it disingrates to a green powder. I had to cut away much of the red wire and solder it directly to the copper (tongue) (post) that comes off the hydraulic pump. I ended up having to break away some of the hard plastic surrounding the post, but am not sure it was necessary. Once the wire was repaired the light went off, but the ABS system would activate at low braking speeds on dry pavement. It was suggested by a dealer's service advisor that I remove and clean the ABS sensors in the front hubs to see if that would resolve the low speed braking activation of the ABS. To do this you will first reomve the caliper and rotor off the hub. Don't forget to support the caliper with a string as you don't want to damage the brake line by hanging the cilper without tieing it up off the line. The rotor comes right off the hub lugs easily. If not easily then gently, I said gently motivate it with a few taps of hammer against the rotor inwards towards the hub. This will break any rust bonding. Then remove the dust shield with a 6-point 5/16" socket. The small bolts are going to be in tough shape (rusty) and would likely spin out with a 12-point socket.

Another lesson learned is be sure to spray plenty of penetrating lube on the Alan screw retaining the ABS sensor in the hub. Let it sit around the ABS sensor in the front hub and go have a Coke or cup of coffee. Clean the area around the sensor well as you don't want anything to go down the hole into the inside of the hub once the sensor comes out. If possible, use a high quality hardened steel Alan wrench as the screw is likely to need some careful persistence to get it to back out.

Once the Alan screw comes out carefully rotate and pull the ABS sensor straight out with a pliars. There is an o-ring seal around the sensor that makes pulling the sensor out of the hub a challenge. You might use a straight blade screwdriver to pry it up, but be careful not to crack the plastic when doing so. Don't rock the sensor side to side or back and forth. I broke the outer plastic housing off the sensor tube that projects into the hub by rocking back and forth while pulling. Instead I recommend gently rotating it and pulling it with a pliars. Additionaly slipping a straight blade screw driver underneath it to carefully pry it upwards might do the trick.


I was told by a service advisor friend that the front ABS sensors on a 2000 F-150 4WD should have 500 Ohms of resistance between the two terminals if you would like to do a diagnostic test. I believe less resistance concludes a failed sensor.

This friend has a 99 with the low speed braking problem and he did not have success after replacing the front sensors. He was speculating that there was a crack in the ring of teeth that the sensor reads inside the hub. I’m not sure if he tried replacing the rear ABS sensor or not.

The rear ABS sensor can be the culprit causing the low speed activation of ABS. I've seen threads mentioning rear ABS issues coinciding with speedometers not working while other threads don't mention having a speedometer problem with their rear ABS sensor issues. My speedometer is working fine. I will follow through with a post when I get the new sensors in and determine what caused the low speed braking activation of the ABS.

I ordered a Motorcraft replacement front sensor- $125 for the one I broke and Motorcraft rear sensor-$24 from Amazon. (as of 2/24/12)

I highly recommend getting the Amazon.com prime shipping membership for $74 annual. Because I have this, I get free two-day shipping on most items and $3.99 overnight shipping per item on most items. I'm expecting the sensors in less than 24 hours time at or near rock bottom price available anywhere! Tax free and free shipping at Christmas alone pay for the membership at least 5 times over. Plus you don’t burn gas shopping and don’t have to leave the house!

 

Thanks for the lessons! I've got the ABS light on in my truck (01 f150 4wd). I noticed last time I was changing the brakes that the sensor wires had actually been cut somehow (angry ex mistaking them for brakelines maybe?), so i'm on the hunt for a new one soon. I'll have to check amazon being that I also have the prime membership, which is incredibly awesome.

 

My service advisor friend took the truck to his dealership for the pros to figure it out.

There were two needed tasks I was unable to complete and figure out. The ECU (electronic control unit) that mounts on top of the HCU (hydraulic control unit) needed to be programmed to the trucks computer by the dealer.

The other problem I had was one of the front wheel sensor wires was melted to the the state of an open circuit or short against the exhaust manifold.

In summary, if your ABS light is on...

1. run jumper wires to the electrical hydraulic pump by unpluging it from the ECU. This will tell if one of the wires are corrodid down to a power substance (open circuit). If motor does not run, repair hydralic pump wire with sodder or any sturdy means and cover with shrik wrap.

2. visibly check your front sensor wire harnesses for possible damage from exhaust manifold.

3. check the resistance between the two leads of both the front ABS sensor wires at the plug and verify results from specifications in my original post or from auto repair reference at your local library called (All Data) for your vehicle.

4. if you get a diagnosis code indicating the ECU needs replacement, be prepared to drill out the four torks screw heads that mount the ECU to the HCU. They will be likely rusted out. Replace the ECU from an online resource called Silverstate Ford. They are hundreds less than most dealers list price. Also be prepared to have the dealer program the ECU. Don't turn in your old ECU for the core refund until the dealer has a chance to use it for programming the old ECU. It usually can be done without it, but it might save the mechanics some time and you some money if the don't have to do it from scratch.

5. if you end up replacing the HCU, the hydraulics might need to be bled from the dealer.

6. if the ABS system activates at low speed braking, you might have a front sensor problem or possibly may need to have a newly replaced ECU programed into your vehicle, if not already completed. Another possiblity is the rear sensor is bad. a spedometer not working may accompany a rear sensor problem.