Jim Grant's Tech Tips

99 Mazda Protege, Check Engine Light
Q: I have a problem with a '99 Mazda Protege. It was bought as a Demo and now has 27,000 miles on it. No problems until now. The check engine light comes on and stays on. There are no detectable or obvious problems. It runs fine but what could be the reason for the check engine light? My wife had put below recommended octane gas in it recently. Could that have done it? I inspected all the fuses and they were good--this made the light go off for about 4 days. The fuel cap is tight. What should I do?? Paul

A: Paul, you can’t blame your wife for that one. When you were checking fuses you most likely pulled a fuse that was the power supply for the computer’s memory. With no power, computers can’t remember anything. The problem must be real because the light turned back on. What should you do? Have your technician plug into the computer and ask it why. After which the mystery will be gone and the diagnosis and repair can be made.