ok I have a check engine light it has been coming on and off before I had my car down for the last four months and now its back on this is what my scantool said:

P0422 main catalyst efficiency below threshold (bank 1)

I don't know if the sensor is bad or my cat is down for...

so please help me my fellow tiburon lovers

bump...

come on guys help me out

 

Do you have a stock exhaust? If not, what do you have?

 

Either cat or rear O2. Usually a bad rear O2 would set a code for it though. The P042x codes are never a good one to see.

 

It might be your catalytic converter. Mine has 80,000 miles on it and it's still good.

If it is your o2 sensor, just replace both o2 sensors. Sometimes the front o2 sensor giving incorrect or slow values will cause the computer to misinterperate the rear o2 sensor's values. Even though the code states rear o2 sensor, you should look at the front o2 sensor if you have never changed it. Front o2 sensor gets more wear and heat then the rear o2 sensor and it goes bad first.

 

REDZ- I have obx headers-carsound cat-under axle exhaust....

Also i replaced the front o2 sensors around october of last year so i know it is good...

So it either my cat or rear o2 sensor...

 

As my exhaust guys told me, o2 sensors RARELY if ever go bad.

Very rarely.

Replacing them is just throwing money at the problem.

Now, tell us about your o2 setup. Did you put one after all of the collectors joined and one AFTER the cat?

did you extend the wiring? If so, how?

 

Im going cat. If it was the wiring you would have a code for high or low input or whatever and if it was the sensor usually it would have a sensor code because it checks the sensor. How many miles on the car/cat

 

After looking at the code again, it's the same one I threw after my new headers and such went on.

It went away after I got the new exhaust on and never came back.

 

i had this code too when my cat was in the back of the exhaust. (??????) i went back and got the cat moved up right after the resonator where there was more heat and the code went away for good.

that didn't eliminate my crap O2 low voltage problem though but at least the cat is out of the way. if it's up front like it's supposed to, i'd say the high flow cat is the problem. a mechanic of mine told me that there's a reason stock cats cost so much because the quality of it is so much better and it filters out more toxic emissions. you might just have a cheap cat.

 

From what I've learned lately, low voltage will come from poorly extended wires, or damaged wires.