need a little help with my WRX

for some reason today my check engine light came and i dont know why. i just got the car in march, all i have had done to it is have a new exhaust put on which was at my subaru dealership. so i was just wondering if anyone here would know why it might have came on.

whoever installed it probably forgot to put the oxygen sensor back in, or if it is installed properly it could be defective or dirty.

yeah im going to take it in on my next day off, i was just wanting to know some of the things that would make it do that before i took it in.

Is the exhaust catless by chance?

no its a catback, and i have had it on for 4 months now, but yesterday was the first day the check engine light came on :-(

did u recently get gas before the light came on? subarus have a vacuum sensor on the fill tube that lights the check engine light if you didnt tighten the cap all the way, if the car runs fine then just disconnect the negative terminal on your battery let it sit for 5 minutes, put it back on if the light is still on its something else, but if its for the vacuum sensor...PROBLEM SOLVED

I've made that mistake before...not tightening up the gas cap enough. make sure it always gets tightened well. You could always stop by Autozone and have'em check for codes. That'd at least give you an idea as to what's wrong.

yeah i think the gas cap was the problem, but in the book it said just to tighten it and after you drive it a few times it would turn off but its still on :-( so i'll try disconnecting the negative wire and see what happens. thanks for the help :-)

yeah it was the gas cap, it only took 5 days for the check engine light to go off lol, thanks for the help :-)