I've been out for a while but in the mean time I had flatbed installed on my '92 F250. After the install the rear abs light comes on at 38 to 40 mph and stays on for the remainder of the time the truck is on. My cruise control and trailer electronics still works as they should and I have replaced the sensor on the differential, but the rabs light still kicks on around 40mph. Does anyone have any ideas about to satisfy the Rear ABS wiring? Thanks.

 

may not be wiring, have u check to make sure the ring isnt warped back there?

 

Are you talking about the speedometer ring? I have not looked at that, but the speedo has been verified as still being correct.

 

I think its in the rear end, its what that sensor is actually reading, and if they get warped they cause issues.

 

Stop guessing, pull the codes from the RABS controller.

 

After a few years of just living with my RABS light coming on at 39mph and having a little glow from the LED taillights, I decided to play with the issue again. Turns out that LEDs require some kind of resistance or otherwise a system designed for incandescents will think a bulb is out (I didn't have a rapid flash). So, after doing a bit more digging, I found that some people with our OBS trucks had the same issue when upgrading the factory bulbs to LEDs on their conventional beds kinda like me on my new flatbed with LEDs. My solution came be getting some Phillips 6-ohm resistors and wiring from the flasher to the ground and at that my problem went away! Now, I only did the left side as that seems to be good enough and I don't know if I'll need to go back and add the other resistor to the right side or not. But long story short, if you go to LED taillights, you'll need resistors more than likely.

 

These trucks with an electronic automatic transmission require resistors when switching all 3 brake lights to LEDs in order to maintain torque convertor lockup. I have not heard of there being an issue with the RABS before but am not surprised either.

 

I have seen threads about LED lights causing problems with electronic transmissions. Glad you got it figured out. Out of curiosity, did you do what rla suggested back in 2017?

 

Haha no, I just dealt with it. The problem was funny too; if I plugged in a trailer that was still running incandescent lights, it didn't have an issue. But if I ran trailers that have LEDs, the trucks taillights would glow and the RABS light would come on at 39mph.