ive been smelling fuel inside the cab of my car. and a engine code of p0420 appeared like a few days later. what on earth could be wrong?


2002 oldsmobile alero GLS

 

id like to add that my cat was replaced a year ago due to a clog

 

Try reading this:http://http://www.obd-codes.com/p0420
The rear O2 sensor is only used to check cat function, it doesn't affect the fuel-air mixture. That is the job of the front O2 sensor.
I would look for an exhaust leak first since that is a dangerous condition if you have one.