P0420 CODE

fumey · #1 11-21-2005, 07:24 PM

Had this code pop up about 40k miles ago, cleared it and had no problems till another 40k miles. This time , I cleared the code and it only took about 1200 miles before it showed up again. Just wondered if anybody ever actually had to replace their converter . I'm going to check the O2 sensors , maybe foul out my plugs with the sea foam treatment ( wish I'd saved the old ones -maybe now I'll try those iridiums) , clean the MAF to see if any of this helps, but I'm kind of bummed cause I think my high mileage may have cooked my cat. Should I be worried about the engine? Is there a possiblity that maybe the CPU just needs to be upgraded? Help? THanks.

dezert_rida · #2 11-22-2005, 08:28 PM

If your having a cat efficiency code, chances are the cat needs replacement. Most cats last 60-80k.

The ECU does not need to be upgraded, the cat does.

WATRD · #3 11-25-2005, 12:12 PM

From the FSM, possible causes of a P0420;

Gas leakage on exhaust system
A/F sensor (bank 1 sensor 1)
Heated oxygen sensor (bank 1 sensor 2)
Three–way catalytic converter

Check your oxygen sensors before you worry about the cat.

BirdmanP · #4 11-28-2005, 10:33 PM

Good Luck. I still can't get my P0420 Code to go away. I can delete the code and it just comes back. I have done everything. New Cat, both 02 sensors, and no leaks. I did put a header on it, but I don't hink that has anything to do with it if there are no leaks. Sometimes it will stay off for weeks at a time, and sometimes it will come back in a day or two.