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Seasonal Check Engine Light?

Hi Guys,

Here’s one for you. I have a 1998 Subaru Impreza Outback Sport, AWD, 5spd with 101k miles on it. The car is in generally good condition, but last fall (around beginning of Oct '07) the check engine light (CEL) came on. I checked my owners manual which said to make sure the gas cap was on tight, then wait a few days to see if it would go out. Well, it did go out after a week or two, but came back on again after another couple weeks and stayed on all winter. I tried changing oils, brands of gasoline, octane levels of gas, fuel injector cleaners, etc. Nothing seemed to make any difference, but the CEL wasn’t accompanied by any loss of power or other problems.



I’ve not put many miles on the car this year (maybe 5000 since 9/07) so I didn’t worry too much about the CEL since it wasn’t flashing. When spring rolled around though, much to my surprise, the CEL went out and stayed out.



All was well from roughly late April or early May until two or three weeks ago (around the beginning of October 2008) my wife mentioned that the CEL is back on again. The car appears to be running quite well (as always). I’ve changed the oil, but haven’t bothered trying the different brand of gas or higher octane gas since it didn’t work last fall.



Do you have any ideas about what could be causing this? The owners manual says the non-flashing CEL means a fault in the emissions system, so I’d guess that the reformulated (cleaner?) summer gas might have something to do with it, otherwise maybe something to do with the atmospheric temperature/humidity? (The car sits outside all year round in Pittsburgh, PA.)



Any help you can offer would be greatly appreciated.

Stop by the local parts store. Most of them will read your stored fault codes free of charge.

Skip the wild guessing.