I had my CEL light coming on after 5 minutes, then going off. This went on for 30 days. Then one day it was on all the time. Still, I had no symtoms of anything being wrong except for a few times when the idle was at 1200; a definate 1-2 second miss on the freeway in 5th; and a buzzing on my stereo. The CEL said it was the O2 sensor plus a couple other things. I found when I wiggled the ground wires which connected on the battery shelf and going down to the underside of the engine, it would miss. I ran a new ground line to the firewall about a foot away. It solved everything but the stereo buzz. Soooo, I'd check the ground, especailly if you travel over bumpy roads (like mine is a dirt mile long driveway with lots of dips and switchbacks. It just seems that most of my problems are from shaking the car too much.