Hi guys. I'm new here, and new to Ford pickups. I have a 1990 F150 that has a Rear ABS light on all the time, and the manual that I have for it is a Haynes manual which is doing me no good whatsoever. When I turn the key on the light comes on for a second, then flashes off then comes back on and stays on. This tells me that the module is doing it's self test, correct???? I switched the sensor on the differential with a different one out of an F150 that I have for parts and it didn't help. I have a plug under the hood by the fuel pump relay that says RABS test. It is round with 2 pins inside it. Is there a way I can get a code out of it by grounding this out or something? You guys are going to have to point me in the right direction. This is my first Ford pickup, I have had an old Chebby pickup for a long time, and am a very capable mechanic, just not familiar with Fords is all. I'm ready to learn though.


-Justin

 

I'm not sure how the '90 is, but on my '87, you're supposed to be able to ground a wire under the dash out and get the abs light to blink out a code. Try jumping the two wires in the test connector you found and see if that works. The rabs module only stores codes until the engine is turned off, but since it's not an intermittent light, it should set a code as soon as the light comes back on the second time after you turn the switch on.

 

I tried jumpering those two pins together and didn't get anything. What does the wire under the dash look like? Is it a black with orange stripe and a flat connector in it?


-Justin

 

I'm not sure, but that sounds about right. It should be near the parking brake pedal if it is there. It's just an end of a wire with a square-ish plastic connector on it.

 

I'll try grounding that bad boy out and see what I get. That is correct, the one I'm talking about is by the park brake pedal and is a squarish thing. I'll do that as soon as I get home from work. (night shift tonight ) I'll let you all know what I find out.


-Justin

 

OK, so my manual says I should have a connector with a black with orange stripe wire on it, and a mating half to that connector with a red wire on it. According to the drawing I have in my Haynes manual the red wire goes to the wire that runs from the fuse box to the brake switch, which would mean there is power going to the test connector at all times. The problem is that I have the black with orange wire and connector, but not the other half. (Remember before me this thing was worked on by an idiot ) Could one of you guys check yours to make sure that you have the two halves like I described? When I turn the key on and then ground out the black with orange connector I get a code 44 (four fast flashes, space, four fast flashes, space...etc.). I am thinking if I connect a wire from constant 12V to the black with orange wire I will be OK. What do you all think????


-Justin

 

I don't have anything plugged into the connector either. Here's what I have for code 4, from the Chilton's manual:

Check the electrical connection to the ABS valve on the frame rail near the fuel pump.

 

My truck did not have anything connected to the orange/black one either. I wouldn't connect anything to that thing.

I've got the yellow abs light and the red brake light and the 4 flashes. There's some tests that you can do on the rabs valve connector that I'll try and letcha know what's up

 

What are the tests for the valve?

 

I have no red brake light, just the RABS light. Further detective work reveals that the drawing that shows power going to the test terminal is wrong, because the actual wiring schematic shows the test lead has nothing connected to it. So now I am thinking that the problem is in the valve switch somewhere. This is interesting however. When I got the pickup the red brake light was on as well and I found that the wire to the park brake was disconnected (didn't matter as far as the light goes) and that the wire to the brake fluid level sensor was disconnected because the fluid level sensor was bad. I replaced it and the red light went out. So now I am where I am. I see I can do a lot of tests just to see that my selenoids aren't burnt out or if there is a wire shorted so i'll do them first. It'll be a few days since I am working 12+ hour days and am sick on top of that. (winter cold, not flue ) Thanks for now.


-Justin