P0420 came back!

So its probably best just to replace the cat. If it is bad. So how does one know which cat is bad? If I do the diagnostic will it tell me?

 

Most muffler shops have cats for cheap. I won't be oem but it'll work.

 

Yeah, Im ganna be calling him tomarrow and hopefully he can look at it, and find out whats wrong. But Im hoping its not my front cat, because I we had to weld that new flange to it for my TRD headers, and that was a pain! He wont be happy If we have to do it again!

 

Hi!!

I've been reading A LOT on this P0420 problem and found out a few good thing you might like to know!!!

I lot of people have the same problem that we do, some changed everything related to emission system. Cats, o2 sensors, MAF, MAP, Temperature Sensor and still had the light coming on!!

On thing that not a lot a people think of checking is the Ethanol rating in the gasoline they use!! Toyota tacoma are set to use Gas with less then 10% ethanol... So what i did is I empty my tank and filled it back with ethanol Free Gasoline, unplug the battery to erase the codes and Guess what, no more light...

The problem with ethanol is that it doesn't burn like regular gas at all and our O2 sensors do not reconised the exhaust gas so your check engine light turn on!!!

I was using Gasoline that had 12% Ethanol and didn't know it!!

Try that and let me know what happens

Thanks

 

Do not get a magnaflow! I bought one that was guaranteed to pass OBDII. It did... for a week. I gutted it and bought a sim from URD. I pass emmisions everytime provided I do not have a leak.
When I installed my headers I removed the first cat (closest to motor) I never threw a CEL. The 1st one is a pre-cat I believe. This may or may not work on yours.