Engine Light P0420 code ???

So my engine light has came on, gone away and is now back again.

The code is P0420
probable cause reads:

1. Air leak in exhaust before rear HO2S
(Heated oxygen sensor) Bank 1

2. AF sensor error

3. Fuel system fault

4. Faulty Catalytic converter

Any input from you guys would help out a lot if you have had this problem. Dont want to just start replacing with out an educated guess.

 

I had that code for a while on my 96 Tacoma. I went through the steps of changing all the exhaust gaskets, looking for leaks and what not. That didnt help me. I changed out the o2 sensor and that fixed my code. You may still want to look for leaks though...

 

Check it

 

Mine was on this past summer. Checked everything rigorously for leaks. Bought a new Denso O2 sensor, problem solved.

 

Ok guys, I just changed out the oxygen sensor and when I started the truck the light was still on. Do I need to reset the engine light by removing the neg battery? I hope so I need to get through DEQ in the next day or I will have to buy another trip permit.

 

I'd reset it. I had to replace both o2 sensors on my old truck.. It should clear itself eventually but resetting will be faster. If you still have a problem it'll come back on.

You will likely need to drive for a while for all the monitors to show "ready" - unsure if Oregon will fail you but many places require monitors to all be ready.

 

Ok thats what I was thinking, I reset it before I went and bought the sensor and went through deq but it wasnt ready yet. Was trying to cheat because ive done it before with an older car. I'll try to reset but hopefully it doesnt come back on and the sensor is indeed the problem

 

clean your MAF....im willing to bet it will get rid of your code. I spent a fortune one time trying to clear that code...new o2's, new cat, etc...an $8 can of CRC Maf cleaner did the trick

 

when mine came on, it was because of a bad cat. so i installed a URD O2 sensor simulator and deleted the rear cat completely. no check engine light on since. just an idea

 

Thank you guys for all the Help!!! The Denso 02 sensor fixed the problem. I had to reset the engine light with the neg battery wire and drove it all over hell yesterday and it passed DEQ. Thank you again.

 

an exhaust leak after the cat caused my P0420 so it's more than possible, 125,000 on the sensor.