Re: ive got two questions...
I would start by cleaning all of the connections involved with the wheel sensors with contact cleaner and reassembling with a liberal amount of dielectric grease.
At this time you could also measure the resistance of each sensor with an ohmmeter. A passing test is a resistance of 800-1500 ohms.
-1992 Ford F-150 (winter truck)
-1998 Lincoln Mark VIII LSC (fun car)