po421

[mrstee75]

CEL is driving me crazy. First it was the map sensor then large vacum leak, now this po421 code. is it my cat or the oxygen sensor? replaced my cat last year, do they go bad that quick?

 

[tweety2300]

Your maf being bad caused the car to run rich which messed up the Pre cat. Search for the non fouler trick to save your self some money

 

[JReichle1]

sorry for the bad news, p0421 is a code for bad cat converter...

 

[PROTEGEBORI00]

I STILL HAVE THIS CODE 0421 and 0171 TOO. OBX HEADER WITH NON FOULER, WEAPON-R SRI (WITH TOYOTA MAF SENSOR), NGK WIRES AND COILS BOOTS, NKG SPARK PLUGS DBL PLATINUM!! I DONT KNOW WHAT ELSE TO DO!!! PROBABLY IF I PUT A BOMB INSIDE THE TANK GAS IT MIGHT SOLVE THE PROBLEM!!

 

[tweety2300]

You shouldn't have it with the non fouler, dumb question but which o2 sensor did your put the non fouler on?

 

[PROTEGEBORI00]

After cat

 

[PROTEGEBORI00]

But if i plug in the obd2 scanner the cat conv said ok!! So i dont get it!

 

[calikid2609]

you have an o2 on the manifold, and one after the cat. 0421 i think is bank one on the manifold.

 

[tweety2300]

P0421 is a code for the precat being bad so it's the 2nd one it could be a bad o2 sensor as well

 

[PROTEGEBORI00]

O2 sensor




OK which one i should change?? Or both??

 

[calikid2609]

i'd say just change both....unless you just have the money for one