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!
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....
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. :(
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.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.