Why would the driver side brake light not work when the passenger side brake light as well as the running lights and turn signals all work on your 1999 Jeep Grand Cherokee?

Most lights on modern cars are function specific - one bulb for the brakes another for signalling, etc.... Find the bulb that is loose or blown and tighten or replace it.

AnswerPerhaps the first thing to consider would be that the bulb is burnt out or loose. AnswerThe following site discusses all lights in the Jeep Grand Cherokee, and includes pictures and diagrams on how to access them so that bulb changes can be made: http://www.wjjeeps.com/lamps/lampsrem.htm#EXTERIORREM

Scroll down to find specifics about removing the rear housing so that the brake light can be changed.