RayLyZ06

I believe I finally found the culprit. I've been getting these codes randomly fire sometime now. Stopped for gas today and checked under the hood and realized the PCV vacuum line on the throttle body didn't have a hose clamp. 2 hose clamps-$4.50 and one cut finger fixed this nagging issue. Hope this helps someone out. No idea why there wouldn't be hose clamps there in the first place.

skip1980

its possible that may fix you fuel trim codes (p0171 p0174) but i doubt that would have anything to do with a p0420. A code p0420 is a bad catalytic converter.

RayLyZ06

Skip1980 if the car is running rich it can effect the cat. Vacuum leak plus bad 02 sensors can throw a false cat code. If a $5 part keeps a p0420 code from coming back I'm good with that.

skip1980

The p0420 code will set because o2 sensor 2 is not seeing a large enough drop from sensor one. The only purpose of sensor 2 is to see if the cats are cleaning up the exhaust enough if not it will set a p0420. Sensor 1 is used for fuel delivery.