Here's the deal, I have a 1988 F-150 4x4 it is equipted with rear antilock brakes. just recently I have started having a few problems with them. when you turn the key on and the computer runs a check it does not activate a warning light but when you get on the brakes, the rear wheels will lock up and the both the yellow rear antilock light and the red brake light will illuminate. if I turn the truck off the lights will go out and stay out till I have to get on the brakes again. I did a serch on this problem and decided that I should pull the codes before just randomly throwing money at the problem.

My question is how can I pull brake codes, I know how to pull engine codes but am not to sure on the brake system.

Also, is there anythng obvious right away that i should check for first?
please let me know something, thanks