[HondatechAV6]

all 03-04 civic hybrid models can have the ecm updated for this problem. the computer incorrectly codes a p0420(cat deteriorization) based on unusual driving habits using it's current software. you can't pass emissions, even if the light turned on, then turned off.

take it to any honda dealer and they will update the computer, ask about SB#05-028. keep in mind this may not fix your problem, but it's the first step. the computer needs to be updated properly before it can test the cat. also, you have two cats on your car.
but if the light came on with p0420 - you need to replace the exhaust manifold/cat and update the pcm.

most likely it will keep the light off though.