Carefully check all of the grounds in the system. make sure that they are tight. Loosen them up, then retighten. This will clean the connection and assure tightness. You might also consider a battery. This is the time in the life of the vehicle that it will probably need one. If the battery is having problems, the internal resistance will fluctuate, causing the ECM to chase the system voltage by controlling the alternator. This is good advice for anyone driving a vehicle with OBDII monitoring. Fluctuating brightness from the lighting or blowing out bulbs is indicative of fluctuating voltages. Batteries are the first suspect in this eventuality. Ray