I'm just now getting into troubleshooting the ABS system on my 1996 F250 4x4 as the idiot light has been on since I bought the truck. First off, the brake fluid is full.

I think I know the basics of the system. I figured I'd start up front by the master cylinder and work my way back. I pulled the electrical connector that plugs into the side of the master cylinder. I turned the key on and hit each wire with a test light. Nothing. I had the key on and hit the brake pedal and checked the wires again. The test light does not light up at all on any of the three wires.

Am I supposed to be getting any current through these wires? Have I found the main reason why the light may be on (no power to the system)?

 

So no one knows if these wires should have any current running through them and when?

 

Ther was a thread running on the brake page some months ago about this. It seems that there should be 12v on one of the wires at the M/C plug which, if the fluid level sensor is working correctly, is then passed via the level sensor to the RABS computer. Without this voltage the computer turns the warning light on and disables the RABS. I don`t know but I assume the voltage comes from the fuses.

 

Ok, here is what I just found out. I tried to pull the codes from the ABS computer by disconnecting the RED wired connector from the black/orange connector from under the right side of the dash and grounding it koeo. Nothing. Zippo. I turned the key on and the light did nothing.

Long story short, I checked the fuse block under the hood and discovered relay 5 was missing. I was always missing but it turned out it controled the fog lamps for a Lightning and the freaking ABS pump. A few questions:


- Would the lack of the relay cause no voltage to be running through the wires on the master cylinder wires mentioned above?

- Would the lack of the relay cause the computer not to spit any codes?

- Is the ABS dash light itself triggered by the ABS computer or the EEC?

- The wire that connects to the black/orange ABS code wire supposed to be red? I thought it was supposed to be black.

 

first, you do not have abs you have rabs.

second, you have no abs pump because you have no abs.

the rabs is under the truck below the drivers feet and is very basic.

much has been written on this and an advanced search will get you much info.

 

NO, there are no relays in the system.

NO, there are no relays in the system.

RABS computer.

Yes it is RED.

Here is a diagram:
http://i54.photobucket.com/albums/g9.../1996RABS1.jpg