flyingchappy

CEL came on and I had it scanned at the local Autozone. Indicated a P0302 misfire but we didn't clear with the scanner. Drove it home, parked it for about an hour, started it up and the CEL wasn't on. I don't think I ever saw CEL clear itself. What gives?

Ed Burdell

I get a CEL once or twice a year - usually just around the time of year when I need to get an emissions inspection! They have always cleared by themselves after some drive time. Sometimes it takes a few days, but (knock on wood) they always do.

uicnick

The way these control systems work involves increment/decrement counters. So if you have a condition which exceeds a limit, there is a given programmable (calibrated) number of times that you can exceed that limit before a fault sets. Similarly, if a condition is below a certain programmable (calibrated) threshold, the counter will decrement and any number if increments you have reached will be reduced for each instance. There will be a history of inactive faults that can be viewed that will show you the faults that were previously active. That history should never clear itself, but yes a fault can change states from active to inactive. The key cycling is an entry condition to enable the state change. Yay-yay!