One problem related to brake light on has been reported for the 1998 Lexus GS300. The most recently reported issues are listed below.
Purchased a 98 Gs300 six months ago and my vsc, abs, brake light and check engine warning gauges came up and will not go away. Did some research and found out the brake master cylinder, throttle position sensor and throttle position actuator were the problems. With these few items gone bad my car produces little to no power during acceleration. The car barely gets up to 45 mph with acceleration pedal all the way down to the floor. With the vsc gone bad there is an alarm that stretches to uncomfortable hearing levels that' hurts like the devil. My car will literally stop in the middle of cruising and won't pick up any speed unless I have my foot pedal all the way down to the floor, which also often times causes it to turn off on highways, all types of streets and other areas. Also with these items gone bad my car shifts so hard to the point where it jumps whenever I shift into any position. All in all the vehicle, I feel , is too dangerous to drive at this time.