I have an 1988 F150 4x4 with 302V8 and RABS I antilock brakes. The Rear Antilock light comes on when starting the truck as it is supposed to, and then goes out in a couple of seconds. However, in about 30-60 seconds the light comes back on and stays on. I've found the black with orange stripped wire with a connector on the end just behind the parking brake pedal. I've tried to ground this out to obtain the RABS I codes, but the light just keeps glowing. Is this connector with the black/orange strip supposed to be connect to another connector???

Any help would be appreciated. I did top of the master-cylinder with fluid to the "max" line, but the problem still occurs.

Thanks

Rob

 

On my 87 F150, I had the same problem, turned out to be the little computer module mounted on the frame, was easy to replace after I properly grounded those wires you spoke of, I did have a slight problem finding a good ground.

 

Oh, forgot to mention, I believe I had to disconnect the negative battery cable to reset the computer before I could ground the wires.

 

I'm not too familiar with break system types... like the RABS I you mentioned.... but, on my 1993 F150, i too got ABS warning lights after start-up. I would start up my truck and after 20-30 seconds, the ABS warning lights came on, i first came to this site and they all recommended the same procedures. Some mentioned disconnecting the ABS system all together. But i refused to do any of those first.

It turns out that the actuall breaks were really "wacked out." My front break pads were uneven and running low, the front rotors were slightly warped, the calipers were giving out, the rear drums were leaking, the shoes were cracking a bit and were down to their limits, the drums were now too big for the shrunkin shoes explaining why the ABS was giving me warnings

This is just one scenario though... i would suggest that you do a complete break inspection if you haven't done so already... then you can dig into the eletrical stuff.

P.S. after replacing most of the breaking system components...except for the rotors... i have been getting some serious shaking during high speed breaking....

 

I'm such an idiot... RABS is an abreviation of Rear Anti Lock Breaks... boy i feel stupid. LOL :P

 

Rob88,
Ive seen this problem a few times and here is what I have done to remedy it . Locate the sensor for the Rabs mounted on top of the rear end , its right on top with one bolt holding it in place . Remove the connector and unbolt the sensor .Most likely what is happening is metal has deposited on the magnet and the signal from the trigger wheel / sensor isnt getting thru all the time . All you have to do is clean the magnet up and reinstall it .The brakes are fine otherwise are they ?
Paul

 

Thanks Paul.

I will try your suggestion about the magnet on the rear axel speed sensor. Yes the brakes work great otherwise.

Appreciate your assistance

Rob

 

I realize this is an old thread, but for those searching for possible causes for similar symptoms I can add another cause. On my 92 Explorer, I too had the RABS light that came on after startup and stayed on. No codes were produced by momentarily grounding the diagnostic connector either. Turned out to be a problem with the 3 pin connector at the base of the master cylinder. One of the female pins had cracked such that a false low fluid signal was being sent to the RABS module. In general, with older vehicles exposed to road salt, I find a number of connector related problems. In my case the shop manual recommended replacement of the master cylinder based on the test results, however I doubted that was the case and was relieved that it was the connector pin.

 

I had the exact same problem with my 88. It turned out that the rotors needed to be turned, but I found out very quickly that one of the rotors had already been turned dangerously over tolerances. Now, I have the same problem again, and I know I need to buy at least one new rotor, but the other one was new last time so I'll just have it turned.
Just my opinion on your brake vibrations. You might want to have those rotor turned.

1988 F-150 Custom to XLT Lariat conversion, 5.0 EFI (formerly 300 I6), 5-speed M5OD, 3.08 rear gears (will be upgraded to 3.55's), Summit headers, Flowmaster muffler W/ dual 3.5" tips 24" long.

Pioneer CD, AC, Tilt, Cruise, Mobile Radio, Lightbar (Force 4 LP6000), Federal Signal PA300 Siren W/100W Siren Speaker. Caution Customizing in progress, Watch for flying tools & Parts!

 

I have a 95 F150 4X4. My problem was the three pin connector on the master cylinder. Wires and the connector itself were broken. Check it out, it could save you a lot of grief.
Bill

 

I had an 87 that developed "gremlins" in the rear antilock brake system. My friends at the local Goodyear took a look and found corrosion all over the place, on the sensors, on the wiring terminals, on the parking brake actuator, and on and on and on.

The rear brakes would just suddenly lock up when it was wet outside (raining), and I had antilock brake warning light on from time to time.

To make a long story short, Goodyear disabled the antilock brake sensors and removed the parking brake cable. Worked fine (without the antilock feature).

good luck

 

Just out of curiosity are you running 2 differnt size tires on the back? I had a 90 F150 XLT that I was running 275/60R-15s on the back and 255/60R-15s on the front. I had no problems with this combo and it looked and held the road great. However, I got a flat one day and put on the original spare, 235/75R-15, on the back. Maybe it was something to do with the factory locker rear but I got the RABS light until I went back to matching sizes on the back. Just a thought.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

In some states I know that Texas is one, It will not pass inspection without the parking barake working.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

Here's another solution, my ABS light was on when the fuse was *cough* inadvertently removed instead of the fuse for the instrument panel (damn easy way to turn off the odometer, hehe)
but a bad thing about that fuse, when its out the ABS computer doesn't get power, so I did a nasty 180 spin/slide on the freeway, that was the end of my fuse swapping fun!


1995 F150XL - Reg cab/bed, 4.9L, 5-speed, Metallic Navy Blue/Gray int.
Mods: Tanno cover, bed-liner, 1200 watt Crunch amp, 2 10" Rockford Punch Subs, sony cd-player, K&N Filter, Flowmaster 40 series w/ no visible exhaust exit (soon to be increased to full 3" piping), BFG A/T 31"x10.5"R15 & Rancho RS5000 shocks