One problem related to brake sensor has been reported for the 1999 GMC Jimmy. The most recently reported issues are listed below.
I own a 1999 GMC Jimmy that has had a history of brake problems since purchase. In August of 2005 we experienced "pulsation" of the brakes. Our mechanic told us that the abs system sensor is activating a low speeds. When we try to stop it activates and causes increased stopping distance. I see that there is a recall on 1999-2002 GMC trucks and SUV except Jimmy's. I find it hard to believe that this is not happening to other Jimmy's. This problem is very dangerous. I am going to see if the dealer/gm will pay for it. I sure hope so. I bet that gm did not recall the Jimmy because it sold the most of that vehicle !.