Hey guys. I am a student of automotive technology and am about to graduate. I just wanted to tell everyone that when you are working on your own stuff whatever you do DO NOT clear the codes. I had a vehicle today that the customer complained of the check engine light coming on and off randomly. So they had autozone clear the code and it was an O2 code. Well autozone cleared the code but now they want the problem fixed so it doesn't ever happen again. but since they cleared the codes we lost all freeze frame data. With and OBD II system, when the check engine light comes on it stores something called freeze frame data. It is vital information about your engine like your fuel trim and RPM, engine load, speed, MAF and so on. Tech's can look at this information as a guide to what was going on when the code set and try and get the vehicle back into those operating conditions for intermitten problems. When you clear the codes you erase all this information. So please if you don't have any clue what you are doing don't clear your codes. Once you fix the problem the check engine light will go away after it passes tests from the PCM several times. And after around 40 passed tests it will clear the freeze frame information because the fault is no longer there. So please please don't make our life difficult.

 

I dunno about that man, I would rather not see that damn check engine light then anything!

 

Just tell the customer to bring back the car AFTER the CEL comes back on. There's nothing you can do since THEY had the code cleared (thanks to the putzes at AutoZone).

It it proper practice to clear the codes once the fault has been corrected. See the service manual.


Steve

 

You could be losing money with this advise, turing a day long troubleshooting session into a quick 1 hr job.............