Check Engine Light...again!!!?

2003 Hyundai Elantra with 101,000 miles. Check engine light has come on three times prior- once was the gas cap...twice with O2 sensors.





On Tuesday of this week I took it to Monroe Muffler thinking I needed a new muffler...turns out it was the flex pipe that needed to be replaced. It was replaced and all was good.





Then this morning, driving to a job interview, my check engine light came on. It's solid, not blinking, so according to my dad, it's something to get looked at, but not an emergency/ can't drive the car kind of thing. The car is driving just fine, however. The noise I was hearing from the flex pipe is completely gone. I was quite surprised to see it come on!





The last time the light was on, it reset itself and all was good.





So here's my question...is it possible that replacing the flex pipe may have caused the light to come on? If it's an O2 sensor (as I suspect it might be based on the history), how much $$$- ball park- are we talking to replace it? My mechanic only charges $45/hr for labor...





Thanks!|||have you tried "disconnectin" battery terminals for 30 seconds or so, sometimes the computers don't comprehend sumptins been fixed or even tuned up, til u reset in that manner...Good Luck, I just like to start troubleshooting with the minors out of the equasion....and the cheapest too lol..|||hopefully you don't mind a woman answering you. anyways it sounds like your O2 sensor but make sure that you dont have a fuse lose or a wire that is blocked anything like that will cause the light to come on.


i hope this helped. go to auto zone if u have one and they will look at the light for free.|||i have black tape covering ABS lite and check engine lite....ck engine code was o2 sensors...i spent 200 dollars on new a week lites back...screw it...runs great...i tuned it less than 5 K ago...400 dollars...new wires and all....runs fine..|||Usually it's the gas cap for some reason. My mum had that and then her mechanic changed the gas cap and it went off right away.|||dont worry bout it i have had a check engine light for months


and my ma did to and it ended up bein the gas cap|||Ingnore that somebeach. The **** things stay on all the time and the cars still run fine.|||Just to cover the bases, you've had the oil changed in the last 3000 miles?|||the absolute easiest way to determine what is making your check engine light come on without paying for it is to go to either Autozone or Advance Auto, in which they will check the light for you and tell you what "code" is being brought up. My guess would be that if the O2 sensors were just replaced, then they more than likely just disconnected the battery to reset the light. if that is the problem, and you have new sensors in place, then chances are they will reset themselves over time. also, as i just found out with my car, if your exhaust has some sort of grounding wire on it, it needs to be put back on. i have a 2008 dodge avenger, and after i upgraded the stock exhaust to a bigger one, the check engine light came on, and it was due to that little ground wire. crazy, i know, but once i reconnected it and drove it for a bit, it eventually went off. hope that helps!!!





PS- my old man runs a Monro in Bradford, PA. kinda where i get my knowledge base from... family business... lol|||Sometimes it takes a few driving trips for the light to go out. Check if the gas cap is screwed on tight. If it's driving fine, I would wait a little bit to see if it resets itself. I had my O2 sensors replaced recently and the light came on a day after it was fixed. It has since turned off. I would hold off on taking it back to the mechanic until you're sure there's a problem. There's nothing more frustrating than paying for a diagnostic test only to find out that everything is fine.