Have an 06 Is350 that just got the p0420 code. Does anyone know if this is for the driver or passenger side cat?

 

Passenger side. Though the cat is probably fine. Most frequent cause of this code is an exhaust leak by the Y pipe upstream of the cats, under the heat shield, which slows catalytic converter lightoff.

 

Ha I get this intermittently as well. Ever since i put my stock mid pipe back on.

Too lazy to get under the car and fix the leak.

Since the code only seems to get thrown every so often, I just keep a bluetooth OBDII module plugged in and every time the light comes on, I just clear it using my phone. Takes two seconds.

One day I will fix it.

 

^Have the exact same issue too. It all came about after my PPE header install. Must have tweaked something it didn't like. I only get the code when it's cold outside and I'm driving slowly due to traffic.

 

I'm thinking possibly because I reused the gaskets at the headers when I put the stock pipe back on. Oh well, it doesn't seem to affect performance and is a pretty minor inconvenience. I haven't had the light come on for a few weeks now.

 

^Oh, I used brand new gaskets all-around. Sealed up great, minus the crack in the piping I have to find.

 

The infamous p420 code light. My mechanics favorite. Kept trying to get me to buy a new cat. i was saying no way, what else could it be, and it was an evap code, a leak, and sure enough it was the right side passenger side. My seals were way overdue and worn out and leaking oil bad. I'm so glad i didn't get new cats, the code would just come back. The hoses were still intact, everything else was good. REPLACE THOSE gasket SEALS.