How to erase P0420

You want to use one of these stainless steel angle spacers that actually puts the O2 sensor parallel with the pipe not sticking out of the pipe sideways like it does now You don't want to use a spark plug fowl or adapter this thing you want to use is $18 has a piece of catalyst material in it and it swivels and locks at about any angle you want to set it in there You apply that to the bung or the hole that the O2 sensor screws in now and that's going to make your O2 sensor go from screwing into the side of the pipe to screwing in with the length of the pipe if you will then that space is you and changes the angle and slows down the response of the gas and material getting to the sensor to be scanned. Just look online eBay and everybody I have them in my drawer here sometimes they get used sometimes they don't and as far as clearing the codes with the AP200 you follow the procedure to clear the codes easily you just touch the code and then do a complete clear or whatever it's called and it'll clear all of those codes that it read a minute ago but you really want to check them first and do whatever it is you need to do before you wipe them out when the sunlight goes up I'll bring up my AP200 on the screen and tell you exactly what key presses to make to clear all the codes but it's right there in the instructions and it's on the screen it's kind of like every scanner you use almost as far as clearing the codes and then if you put the spacer in and you just drive the car two or three runs to the store and all if the PO420 is not detected again it I believe will clear the code by itself and it will become a stored code possibly so that if it does it again it can come back but it generally won't have the light on under this condition but getting the proper spacer is kind of key using a spark plug fowler like you see people doing they don't do very well they get red hot not made out of very good material etc could cause you more strife than not.

 

Do you still have a P0420 that shows as 'current' and lights the check-engine light? Or only a leftover P0420 code shown as 'permanent'?

The 'permanent' codes aren't really permanent; they exist as a record that "hey, this problem was detected" but will go away eventually as the car is driven and passes the associated self test a few times.

If you want to chase the permanent code away faster, you can flip to P0420 in the repair manual and drive the "confirmation driving pattern" shown there.

Toyota Service Information and Where To Find It | PriusChat

 

You can reset the code by disconnecting the 12v battery if your obd reader can not do it.

Also try Cataclean it is very good and works.

 

Be sure first (review post #3) whether you're talking about a 'current' code (that lights the check-engine light) or a 'permanent' code.

Disconnecting the 12V battery, or an OBD reader code clear, will clear a current code. Neither of those things will clear permanent codes. Those only go away when the car has been driven and passed its self-tests the right number of times.

A code clear or battery disconnect can in fact take you backwards if you're dealing with a permanent code. You might already have driven enough to be close to the code going away on your next drive, but now you'll be back to square one.

 

Isn't that for Gen 3 and not Gen 2? That's been my experience...

 

Hmm, yeah, permanent codes were a newer OBD-II thing that it looks like the gen 2 ECM hadn't implemented yet. DTC descriptions in the gen 2 manual still have "confirmation driving patterns" in them, but those seem to be only for the mode-6 readiness monitors, and not for clearing permanent codes in that generation.

So presumably a gen 2 driver talking about a P0420 is talking about a current one, with the check-engine light lit.