Thrown Code P0421

[wiley858]

Now, i have put a turbo on my p5 and taken off the cat but the rest of the exhaust is still stockish. the p0421 code reads as this:

P0421: Warm Up Catalyst Efficency Below Threshold Bank 1

My question: is this code caused by the cat not being present before the o2 sensor?

Would getting a high flow cat get rid of the CEL that has bugged me for the last 20k miles?

If i dont get a high flow cat, how would i get rid of the CEL short of putting electrical tape over the light?

[aMaff]

Search for spark plug non fouler trick or mil eliminator (or something like that). I believe that code is because the 2nd O2 sensor is reading that the 1st cat is not there. A high flow will not fix that issue, you need to trick it into reading correctly.

[silverpro5]

Do our ECUs go into a "safety" (aka lower performance) mode when a CEL is on?

ps. sorry for the thread jack. look in the howto section for how to trick your 2nd O2 sensor.

[aMaff]

depends on the CEL. Generally yes