Truck Repair: anti lock brake light, brake warning light, wheel speed

Question
Why is the anti lock brake warning light coming on when i have to brake ? Thx J

Answer
Hi J,
There may be a fluid leak in the system, or one of the self adjusters may be frozen, causing that piston to be unequaal with the rest, or there may be a wear indicator touching. (You didn't happen to mention what type vehicle you have, so I have no way of knowing what all systems yours has).
I have seen the ABS light come on cause the stoplight bulbs in the rear window stop light were burnt out.
A bad wheel speed sensor could cause it, or some other problem inside the ABS system.

Van