ok so i replaced both o2 sensors prob a year an a half ago. about 4 months ago i replaced my high flow cat with a new one (magnaflow cat). now i been driving with no code on and this past month i been getting codes like crazy same two code P0138 & P0141. my exhaust set up is OBX header, magnaflow high flow cat to a glasspack and back to a stainless steel muffler. the sensors are not that old i dont know why they would go on, i heard from a friend that he had the same issue and had to put a spark plug defouler on the 2nd sensor and it went away? any help would be great. also as a side note my car is starting to run like poo and my mpg is crappy.

thank you

 

. . . and those are codes for: ___________ (you left out an important part)

Conventional English typing has a capital as the first letter of each sentence. This greatly aids the reader in not gouging out his eyes with a dull spoon because the text is so hard to read.

 

If your mpg is crap then it could be one of 2 things, 1 it could one of your 02 sensors or 2 check your spark plugs. If you recently changed them and didnt gap them properly it will result in crappy mpg.

 

Sry for no caps lol. I was in a rush at work. These codes are for my 98 Tiburon. I did a tune up about 3 months ago and i gap them correctly. I got the description for the codes:

<u>P0138</u> Heated oxygen sensor (HO2S) 2, bank 1 �“ high voltage Wiring short to positive, HO2S, ECM Oxygen sensor (O2S) 2, bank 1 �“ high voltage Wiring short to positive, O2S, ECM

<u>P0141</u> Heated oxygen sensor (HO2S) 2, bank 1, heater control �“ circuit malfunction Wiring, HO2S, ECM

I am confused about this problem because one min my car does not have a check engine light then one day im driving it and it comes on? Now when it does have it on, it stays on for a long time then it goes off for a day or two, then comes back on?

 

How old is your O2 sensor? it may be the the sensor took a crap finely.

 

The o2 sensor is about a year or two old.

 

I had a (different) code that came on when it felt like it, went off when it felt like it, and turned out to be a failed O2 sensor. Check the wiring in the harness isn't all melted or shorting or worn or some such, then replace the sensor.

If you got any O2 sensor except the OEM unit, blame that. RD cars have a reputation for chewing up and spitting out non-Hyundai O2 sensors in short order.

 

Yea i went under the car to take a look the wiring harness looks good. I am probably just going to replace the sensor anyway and stop at the dealer and see how much they are going to charge for a 02 sensor.

 

Never use 'Universal' type sensors. There....I said it. smile.gif

 

Thank you all for the help so far. Ok I replaced the sensor with OEM. Now ever since March 10 I had no codes and the car drives great. Yesterday the code popped up P0422. So at this point im pissed. I know its not my cat its brand new Magnaflow high flow cat. Now I was thinking, I am going to check my extended 02 wires to the 2nd 02 sensor. I was also thinking is it my 1st 02 sensor I need to replace? I know the 1st 02 is a Bosh? Any help or info would be awesome. Thank you

Cheers