P0420 (catalyst) code

My 2002 Civic Si threw a MIL, P0420 (catalytic converter operating under efficiency threshhold). I'm now very concerned because of the 80k/8 year
catalyst warranty of which my car is now at 79.4K miles!. I cleared the code and it has not come back in ~100 miles. Now I intend to do the diagnostic test in the FSM. It entails start the car, hold at 3000 rpm until radiator fan comes on, then drive 30 seconds in 4th gear between 55-62 mph, and close the throttle for 1-2 seconds and repeat 4 times. I plan on doing this procedure late tonight or tomorrow night when I can do this somewhat peculiar maneuver. My concern is that it looks like it would be easy to get a false negative. Does the step where I hold rpms at 3k trigger some diagnostic mode or is it to ensure a properly warmed engine? Could I do this on the way home from somewhere at operating temp or does the ommision of the 3k step nullify the result? Should I bother sending a dealer or Honda a letter stating what happened in case it comes back after 80k, will it help with a good faith repair? The procedure is supposed to either trip the MIL again indicating a bad TWC or if not, to be considered an intermittent failure where the code is cleared and life goes on. I am hoping for the latter or a replacement before 80k, thanks!
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WHY did you reset it? Your only hope now is it comes back before the 80k. A letter will mean nothing to Honda. Chances are the dealer would have reset it also but you would then have proof it failed before 80k. Since you are playing with an OBDII tester compare the front and back O2 sensors and see if catalyst is not working. Also see if the non-continuous run cycles are complete. It could take a week for some to complete depending on your driving habits. They all got reset when you reset the code. The catalyst efficiency test has to be complete before the code will be set....

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Shucks! In hindsight, I wish I didn't clear the code! Damn you RAMH for making us competent and self proficient Honda owners! :) Unfortunately I have no scanner, just a paper clip. I guess I'll have to try the test procedure and see if I can trip the code again. Could a bad tank of gas cause this? I took a trip up to NJ from VA and got gas from a shady looking Getty, I thought maybe the gas guy just didn't twist the cas cap enough clicks but the code was not the evap canister one. :(
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I had my Catalyst go bad in my 98 civic after a tank of bad gas. Filled up at this place my buddy swore by cuz they gave a cash discount. Also noticed that the fuel smelled like nail polish remover while filling up. Shoulda been my first clue. The whole way home from Regina to Winnipeg the car was bucking and sputtering, about a week later the catalyst went bad. Fortunately Honda covered it. Not before they reset the ECU twice though. I think I got an O2 sensor out of the deal too. They reuse them unless they can't free them from the old manifold.
t
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PS they did try to blame this on the famous loose gas cap, even though the code was clearly for the catalyst. whata bunch of gearboxes.
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The code came back and I have a service appointment for Wednesday, will have about 79,800 miles by then. What does the P0420 usually lead to? Cat, secondary 02 sensor replacement? Both? Thanks.
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