My recently acquired 1991 LS400 taillamp failure indicator lights up (and stays lit) as soon as I apply the brakes the first time after startup. All 8 (the 6 1157's and the 2 high-mount 921's) brake lights appear to be working when I do not have the headlights (or parking lights) on. The six 1157 bulbs also light up when I turn on the headlights by themselves. However, when I have both the headlights and the brakes on at the same time, the rear upper left bulb does not light. I have tried several things, initially just replacing that one bulb, and eventually replacing all 8 brake bulbs. Nothing has worked. I checked inside the taillamp failure box and it looks fine. I once had a similar problem in my 1989 toyota camry and fixed it by replacing a non-factory rear bulb with a genuine toyota bulb. Tried that with my Lexus but it did not work. Anyone have a similar problem? The previous owner changed the battery out just before I purchased it. He also had the power steering rack and pump changed which makes me wonder if the alternator has anything to do with this. The car has 94k miles. Thank you for your help.