I was wondering if the computer stores codes without the check engine light coming on. If so, does Autozone check this for free? I have an '01 Triton and it seems to be switching gears weird. I'm not really mechanically inclined so anything is beyond me. So I was wondering if Autozone would be able to check this for free before brinigng it in somewhere. Any help is appreciated.

James

 

Your check engine light generally lights up only if a code is triggered on two or more consecutive trips or if the problem is continual. In most instances, when a problem evolves, a code is triggered and the computer stores this in its memory. The next time you drive, if the same problem is determined, the light comes on, if not, the code is cleared (remains in the memory of some computers). Thats why the damn o-2 sensor comes on with a little moisture, like driving to a store, buying some bread (or beer) and heading home again. The light didn't come on on the trip to the store, but since it hasn't had a chance to dry while you were in the store, and the trip home is your second "trip" with the vehicle since the problem evolved, the light comes on on your way home. When the o-2 sensor dries, the code clears itself after you drive the vehicle and the problem isn't sensed. So yes, the computer can read triggered codes that don't trip the light. Problem: some computers continue to store codes even if the computer has not yet tripped the light or if the lights gone out. Some others, namely some Japanese crap, actually clears the computer when the problem goes away....

As for Autozone? Can't tell you. But you can buy generic OBD-II sensors for say $50-70 on ebay. Won't determine everything, but beats the hell out of paying $90 for a dealer to plug you in. Most cheap sensors will clear your system after it's been read as well.