I keep getting the engine code PO422
Advanced auto parts told me that it was the oxygen sensor in bank 1 and I have replaced it.
I bought a code reader actron OBDII reader and it says code PO422 Main Catalyst Below Threshold (Bank 1)
I have replaced the oxygen sensor and erased codes but light still comes on.
Any help will be greatly appreciated. When I reset the light and drive The light seems to only come on when I am on the interstate going 75mph. When I am in town light never comes on.
I have just replaced the muffler because it had a big hole in it and noticed that the tailpipe seems to be loose at the exhaust manifold. Could a leak at the connection to the manifold cause this? A mechanic told me that it could be my gas cap.

 

Gas cap could do it. Did you replace both 02 sensors?

 

I have only replaced the one before the catalytic converter. Do you suggest I replace both?
My gas mileage is good. The check engine light only comes on when I drive at higher speeds.
I have a exhaust leak where the pipe connects to the exhaust manifold.
I am not sure if this is the problem or not.
thanks for your help
Troy

 

Depending on how bad the leak is that could be the problem. I would fix any obvious problems 1st and go from there.

 

P0422 is cat efficiency failure. Your O2 sensors are reading correctly and telling you that the cat is dead. A leak upstream of the cat is going to lean out the mixture, making the car run richer than it should, which might be giving a false indication (but probably not). That would be the first thing to take care of. If the cat efficiency code comes back, replace the cat. I got great mileage on mine with that code, all the way up until chunks started coming out of the muffler...

Best of luck!