ABS light won't go off

[Guanfy]

In my '94 B3000 the ABS light won't go off. The truck has Ford's RABS system. The brakes work fine, but the light won't go off. I've pulled the ABS flashout codes and I get a code 16, which is supposed to be a system passed. But if its a system passed... why won't the light go off? I've checked and jumped the float sensor and the light didn't clear. I removed the connector on the ABS valve module and cleaned it and that didn't clear the light. I've replaced the ABS diff sensor and that didn't clear the light. I had a grounding issue in the taillights I thought might be the issue but I fixed that yesterday and the light still didn't clear. The only thing I haven't done is that the license plate lights don't have bulbs installed and I haven't put bulbs in yet. This truck has been converted to a flatbed and is using trailer lights for tail lights if that sparks a thought with anybody. I've noticed that occasionally when I shift into 4th that the abs light will flicker. The few times I've tried to activate the ABS system on purpose the ABS light will flicker very rapidly for a few seconds then go solid again. If the system turns on I should have a grinding kind of feel in the brake pedal right? Can anyone offer insight on this? It's driving me crazy this light won't go off.

 

[adsm08]

The most consistent fix I know for RABS issues is to unplug the valve, remove the light bulb, and get on with life as if nothing ever happened.

The fact that the light flickers some times and there are no active codes makes me think your issue is a short to ground. Most warning lights are powered all the time when the key on and then the appropriate module grounds the circuit when it wants the light on. If the wire between the bulb and the module has rubbed through and is grounded to something the light will be on.

 

[RobbieD]

The only suggestion I can offer, is to make sure that your parking brake light works (red brake light on the cluster, when the parking brake is pressed with the ignition on). My RABS light was on because the rear brakes were shot. After replacing the brakes, the RABS light still would not go out. My parking brake light also didn't work. But as soon as I cleaned the parking brake light switch, repairing that light, the RABS light reset the next time I started the engine.

 

[Guanfy]

The brake light does light up... sometimes when I activate the parking brake. Sometimes the light is dim, sometimes bright and sometimes not at all. I'll check the parking brake switch tonight and see what I can do with that. Another thought is that since I bought it I've never checked the brake shoes in the back... maybe the light is there simply because the rear shoes are worn thin. I intend to do the mustang disc brake conversion back there so that might be my fix. I'll report back what I find from investigating the parking brake switch.

The only suggestion I can offer, is to make sure that your parking brake light works (red brake light on the cluster, when the parking brake is pressed with the ignition on). My RABS light was on because the rear brakes were shot. After replacing the brakes, the RABS light still would not go out. My parking brake light also didn't work. But as soon as I cleaned the parking brake light switch, repairing that light, the RABS light reset the next time I started the engine.

 

[Guanfy]

So I removed and lubed the parking brake switch and that seemed to help. ABS light still on. I did some hard stops on a local dirt road and found that the ABS system is working as intended and activating. It's... underwhelming to say the least but I do feel the pedal pulsing. When the system activates the ABS light goes off and as soon as it turns back off the light goes back on.

 

[Elutheros]

The most consistent fix I know for RABS issues is to unplug the valve, remove the light bulb, and get on with life as if nothing ever happened.

The fact that the light flickers some times and there are no active codes makes me think your issue is a short to ground. Most warning lights are powered all the time when the key on and then the appropriate module grounds the circuit when it wants the light on. If the wire between the bulb and the module has rubbed through and is grounded to something the light will be on.

Yep, that's the way to fix it.

 

[Guanfy]

Still don't have this fixed, but while investigating discovered my rear brakes were shot so I rebuilt them. Also found the parking brake has slop in it so I fixed that by replacing the spring at where the different parking brake cables meet with a spring from a brake drum hardware kit. Still looking into it and i'll keep you guys posted.

 

[Guanfy]

More information to report. I took the truck to a local mechanic who said their diag tool could not communicate at all with the ABS module, so I bought a Cardone reman and installed it. ABS light is still on but I was able to test that the new module is working. I unplugged the proportioning valve and the flash code changed from a 16(system ok) to a 4(prop valve shut) and it went back to 16 once I plugged the prop valve back in. I then unplugged the speed sensor in the diff and it went from a 16 to a 9(speed sensor open) and back to 16 when I plugged it back in. So the ABS module seems to be working at least. In theory now the mechanic's diag tool should be able to communicate with the module and we can make some headway. The last time I took it there they checked grounds and other wire measurements and they didn't see anything awry.