Hey all.
My "05 Elantra cel came on again and it is saying that my upstream o2 sensor is bad. I replaced it on 9/29/11 with OEM which had a 1 year warranty. Well, it is a week out of warranty and now it is bad again. A few years ago I had the downstream sensor replaced, still under Hyundai warranty.

Is there a history to an o2 sensor problem on these Elantras? As a side note, the engine knocks going up average size hills ( not to steep ). Any advice on possible causes?

Thanks for any info anyone can provide, Angelo.

 

It's possible the car has a fuel delivery problem that is causing the O2 sensors to die prematurely.

 

Thanks novasource for quick response.

Can you elaborate a bit further on your possible diagnosis? Does the "knocking" engine up hills tie in to this? The car is in the shop right now having brakes done all around, so maybe I can call the mechanic with some leads. He is an ASE certified mechanic but may not know as much about Hyundai's as you do.

Angelo.

ps My wife usually just makes short trips to work everyday, so the engine might not get hot enough all the time. It takes her about 10 minutes to get to work.