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Discussion Starter · #1 ·
Today when I started the car to go to work the CEL that has been on for a week and a half shut itself off! :thumbsup: I didn't know they could do that, but I'll take it! Now if only I could get the ECU to "block learn" how to make 200 NA WHP :D :D Anyone else here had a CEL (most likely slow o2 response) shut itself off?
 

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yea the old "gas cap" CEL will usually clear itself. Happened twice on my wifes Elantra, she takes it to this "they pump it" gas place and they are always forgeting to tighten the cap.
 

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Discussion Starter · #3 ·
Couldn't be the gas cap I go four to six clicks every time, but maybe it is a similar CEL, that can clear itself
 

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If the original "problem" that the ECU senses goes away, after a certain amount of time it will shut off the CEL light. The computer logs the problem though until the next time its reset or checked at the shop. I'm not sure what the criteria is, length of time or distance driven though.
 

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if its a gas cap CEL it usually takes about 4-7 dayd to clear itself after you tighten the cap....that is a very normal occurance
 

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Go to Advanced Auto parts & get a ACTRON Global OBD II Auto Scanner #CP9135 it is on sale for ONLY 98.88 use to be 127 to 154. I have used this one & it works great at finding the error & listing the code & clearing the CEL light too.

I bought the Equus 3100 OBD II Code Reader

http://www.iequus.com/item.asp?cid=10&pid=3100

Both work equally well & are easy to us. The Equus does a few more tests (but is has not really helped me, at the time they were the same price so went with the one that did more. they are about 119 still.

All cars since 1996 have the OBD II so it will be usefully on any car you will have in the future also check out

http://www.visi.com/~rhanson/obdII_codes-full-text.htm

for the menaing of the codes..
 

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i had that happen and it wasn't the cap...it was the gas tank purge valve...it would go on and go away....the dealer replaced it for free....the same problem happend a few month later and i just had the valve replaced for the second time...and even though the CEL goes away it doesn't really mean that the problem is gone cuz when this happened to me for the second time i just reset the ECU and it was gone...but when i went in for inspection the station couldn't hoockup to the ECU to get the immissions reading mostly likaly cuz of that even though CEL has been off for at least 3 weeks...then a couple of weeks later the CEL came back on. so that's my story
 

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Discussion Starter · #8 ·
What I should have asked was does anyone else with a full exhaust system (header, cat, cat-back) ever have the CEL shut itself off? The last two I have thrown have been slow response from the second o2 sensor. Thats what I meant about not knowing that the ECU could "learn" to accept the flucuating readings and shut off the CEL on its own. If that is in fact what is happening its pretty damn cool though!
 

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No if you have a full system and are missing a cat, without relocating your 02 sensors it wont shut itself off. It will stay on forever!
 

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watson80 said:
No if you have a full system and are missing a cat, without relocating your 02 sensors it wont shut itself off. It will stay on forever!
Makes you wonder if perhaps your CEL is broken. Does it come on when you start the engine?
 

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Heh, my Check engine light came on last year... had autozone run a quick check... said it was the gas cap leaking. Light went off for a few days, came on again- accompanied by a rich smell of gas inside the car. Seems it did decect a pressure leak in the tank.. my dumb ass drilled a hole through the floor pan under the rear seat... with a self tapping screw- right into the top of the tank- funny how the warrenty won't cover retarded accidents. Some JB Weld and a smell screw turned into the hole salvaged a 290 dollar tank- the light went off, and i started smoking in the car again :)
 

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Any error code could reset itself. With OBD II, it logs every error code. When the same thing triggers the comp two times, it turns the light on. IF the problem is fixed, and the comp reads acceptable readings two times, it turns the light off. But, to turn the light off, it must read acceptable twice in a row. Not just twice. So if you have a problem like a slow o2 that reads eraticly, it will never shut off until it is replaced.
 
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