LX, 2.3, 107k, Japan build. About twice a year, it throws a 0420 error
code, which points at 02 sensors or cat failing. Usually after extended
highway driving- almost never in around town use. (2nd car used mainly
for road trips- only put about 4k a year on it.)
Dealer and a good independent mechanic say replacing cat is only
solution, and both say it has to be an OEM cat to stop the error codes.
800 for cat, 150 for sensors (if the old ones are frozen in place), plus
labor of $150 or so. Call it 1100. Independent mechanic recommended just
keep doing what I was doing- pull fuse 13 to reset when it lights up,
and don't worry about it. I only took it in because it re-lit less than
60 miles after being reset. No emission inspections here to worry about.
I'm a little hesitant to drop $1100 on an 11 year old car with current
book value of maybe $6000. Both mechanics say it won't hurt engine or MPG.
It's the cat, not the oxygen sensors.
Sensor problems have their own codes.
The ECM usually ends up running the P0420 check at highway speeds.
The engine needs to be fully up to operating-temperature before the
P0420 test will run, and around-town use often does not fully warm-up
An aftermarket cat will also work, provided it's correct for your car.
BUT the aftermarket cat will have a fraction of the lifespan of the OEM
cat, so the P0420 will return much sooner than it does with an OEM cat.
The independent man has the right idea.
Leaving the P0420 alone will do zero harm to your vehicle and will have
zero effect on mileage, but it will save you a ton of money. Get
yourself a cheap code reader so you can check yourself once in a while
to make sure it's only a P0420 stored, and not something else as well
(and so you can clear the code once in a while).
Just about the only time an illuminated Check Engine light is of any
real concern is if it starts flashing. Flashing means engine conditions
are such that cat damage is likely.
Also see this page I wrote up some time ago:
This page will help you understand the P0420 code.
<unfinished sentence shown above; see below for the rest of it>
...WITHOUT pulling the fuse).
Yanking the fuse all the time will eventually loosen-up its socket, and
possibly cause you no end of grief.
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