Why would my "check engine" light still be on?
 

I have a 2003 Accent that I haven't had any major problems with until this fall. The "check engine" light came on, brought it to a mechanic and one of the oxygen sensors and MAP sensor had to be replaced. A week later it came on again and the other oxygen sensor was replaced. A week later it came on AGAIN! I brought it to a different mechanic who told me the problem was something else because both oxygen sensors and MAP sensor wouldn't all go off at pretty much the same time. He determined a new computer was required so that was replaced. Guess what happened the following week? Yeah, so brought it back to the second mechanic, he brought it to the Hyundai dealership thinking the computer (which was previously used) had to be reset. That was last week, and it just turned on again today.:mad: I commute a fair distance and it seems to come on after 400 km of highway driving. Does anyone know what else it could be? I read that it could even possibly come down to faulty signals from the battery or alternator? During this whole time there hasn't actually been an issue with performance; it runs very well. I'm just sick of seeing the check engine light all the time. Any advice would be really appreciated!

can't help with the light, but could you tell me how much it cost to replace the computer? I have had transaxle problems. I need to know how and where to get a computer.

The computer cost around $300, plus installation, which made the total just under $500. It was a used computer though and I'm not sure where exactly my mechanic got it. He said that brand new directly from Hyundai would've cost almost $1000 (plus installation).

I'm no expert by far but from what you have said it sounds like the same problem I was having with my 2003 accent. Check engine light kept coming on, can't remember the fault code now but it was telling me something about an oxygen sensor. Turned out it was a small pinhole in the exhaust causing the fault which in turn made the check engine light come on.
I repaired the hole with some liquid metal (not sure what its really called) Light has not come back on since.

Thanks for the suggestion. The mechanic is thinking that's what it could be now and will be checking it again this week. Hopefully that's what it is so this can all go away, although it would've been nice if it occurred to him to check sooner.

@SamJ: Take your car to Autozone, Napa, or the like if you have one nearby. They'll read your OBD codes for free, so you can see what is setting your light off. Once you determine that, forums like this can often tell you how to correct the issue. Mechanics/Dealers are required by law to try to correct a problem before they clear a check engine light, so they'll try anything! You may be able to give them some direction.