1999 Honda accord has check engine light on it shows a code 67 or po420 Catalyst system efficiency below threshold. Does anyone know what this means? Car seems to be running fine with 167,000 Vtec 4 cylinder.

 

I have the same code, P0420 on my 1999 as well.

This is what the previous owner told me: The dealer checked it 7 years ago [2001] and said the ECU in the 1998-2002 Accords are more sensitive, and thus, throw codes easier.

Code P0420 is Catalyst System Efficiency Below Thresholh (Bank 1)

The problem is either a) the catalytic converter is toast or b) the O2 sensor is dirty/bad and needs to be cleaned/replaced.

It won't hurt the engine or decrease performance whatsoever, so feel free to leave it or fix it whenever. It's been 7 years and I haven't bothered to fix mine yet...