:cry short story,check engine came out the reader said p420 something to do with the catalystic converter so i changed it both of them. got it from the dealer $800 each.everything went fine for 5 days the light came back and i feel the car with less power and is consuming more gas.the reader said the same p420 i got a 01 with 125k.if someone can help me out with this???

 

Try replacing the oxygen sensors, they might have ruined the cat in the first place. Usually when the cat goes, a malfunction upstream caused it. The cat will quickly fail on a car that only does short trips (<5mi) during its life. If this isn't the case for you, the culprit is probably the O2 sensors or a fuel/oxygen balance problem.

 

If the dealer diagnosed your car then charged you to repair the car and this is still the problem i'd take your car back to the dealer & raise hell..they have to get it right,i'd also refuse to pay another penny since they're one who diagnosed the problem in the first place