I'm getting a code 420 "Catalyst Efficiency below required level" on my 99 durango. Any thoughts on the problem? The O2's are new and so is the PCM. It also just passed our emission test. Could it be the catalytic converter or ???? help please!!

Thanks in advance


Robert

 

replace the cat...or (used car dealer trick!) purchase 1 or 2 spark plug anti foulers drill out the center2 of the anti foulers, remove the o2 from behind the cat and install the antfoulers reinstall the o2 in the antifoulers. what your doing is raising the o2 from the exhuast stream there by not allowing it a full read(keeps the light off)...this works well when you completly remove the cat or are using a race only mag substrate convertor. but beware your convertor is begining to break down and eventually pieces will begin to enter the remainder of the exhaust system(depending on the muffler) they may become lodged in the exhaust system causing a sigificant performance decrease.