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check engine light (04 WRX)

I just bought an 04 WRX with 50K miles. Runs great, very tight.

After a tank of gas, the check engine light went on. The manual (and the inside of the filler door) says to make sure the cap is on tight. I retightened (it didn't seam loose) and after a couple drives, it went out. My assumption is that if the tank looses vacumn, the light goes on. True?

From time to time the light goes on. It seams to come on after a big change in ambient temperature or humidity (unscientifically observed.) It goes out after a few days of short trips.

What do you think? Bum gas cap? What harm might I be doing to the car?

thanks, P

Reply to
Phil & Brooke
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There are literally hundreds of different things that can set a trouble code and turn on the check engine light. The only way to find out which one is to have the car scanned and the code read out. If there is an Autozone near you they will do a free scan, be sure to get the exact code in Pxxxx format. Once you have this information you can search online for troubleshooting help relating to that particular code, or you can post it here for further assistance. Until you have that info we can only speculate on what your problem might be.

Reply to
mulder

Thanks. Does the scan have to be done when the light is on? or is there "memory" regarding the last time it was on?

Reply to
Phil & Brooke

The code will remain in memory even after the light goes out, as long as the ECU is not reset by disconnecting the battery or the code is not cleared with a scanner.

Reply to
mulder

Uncritical CEL lights wil go out after the ignition key is set to the "on" and then "off" three or four times. (Three I think.) The light just goes out because they know it's annoying. The code is probably still in there waiting to be read.

Bet it didn't have anything to do with your gas cap. :)

Do you use octane booster at all?

Reply to
k. ote

I do not use Octane boost. I only use 91+ which is the recommended.

I will try the on-off as you suggest and see what happens. I wish I could find time to have the CEL read.

I figured it was the gas cap because a) it is stickered all over the place (on the cap, inside the filler door, in the manual) that a loose cap will cause the CEL (must be a common problem), and b) I never have a vacumn when I loosen the cap to fill the tank.

Any-hoo. I'll post once I get the CEL read.

thx, P

Reply to
Phil & Brooke

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