My girlfriend’s 2001 Toyota Corolla has a recurrent Check Engine light problem. It has 144,000 miles on it. For the last few years, we have been unable to keep the light turned off. We have replaced the oxygen sensors and cleaned the MAF sensor. Our mechanic can’t find the problem. Every year, for Pennsylvania state inspection, we have to go through a rigamarole to get a waiver. We may not keep the car for much longer, but do you have any ideas?