P0420 What could it be?

jdmvtec93 · Post by **jdmvtec93** » Sun Feb 18, 2007 4:24 pm

Says
P0420 Catalyst System Efficiency Below Threshold

What could be the problem that causes this code?

rensoyka · Post by **rensoyka** » Sun Feb 18, 2007 5:48 pm

1. If you are running a race header, the sensor is telling you that your cat is missing. Install a defouler.
2. If you still have a cat, it's toast.
3. Your secondary O2 sensor may be malfunctioning.

jdmvtec93 · Post by **jdmvtec93** » Mon Feb 19, 2007 4:41 am

ok i am runing a Jackson Racing race header.

do i have to disable the obd11 option?

rensoyka · Post by **rensoyka** » Mon Feb 19, 2007 5:22 am

That's one option, some people choose that one, others use the defouler method. Disabling OBDII will turn off the CEL.