Honda Car Forum

Check engine light came on. Went to Auto Zone car parts store since all their stores have an OBD II reader behind the counter. If asked they will, FREE OF CHARGE, get the code out of the car's computer (the OBD socket is just to right of steering wheel under dash on my 2000 odyssey). My on-board diagnostics code was a P0420 ("catalytic converter bank 1 not efficient enough... blah, blah, blah"). The Auto Zone people can CLEAR the code if asked (and the Check Engine light goes off). They will warn you that "it will come back" if the fault is hard. It MAY NOT be a hard fault: it may not be the cat converter, it may not be either oxygen sensor, it could be an air leak, it could be bad batch of gasoline, etc. etc.--- all of which may produce a p0420 code (high hydrocarbons are detected MAYBE if all the sensors are right). I then immediately did 2 things (based on advice from someone on the net): 1) put triple the amount of usual GASOLINE CONDITIONER into my almost empty gas tank, 2) went to the nearest SUNOCO station and filled up with Ultra 93 gasoline. Have driven some 120 miles so far and no check engine light. This suggests (does not prove) that maybe it was the gasoline I was using recently --- Going back to Shell gas I guess. Anyway, in the meantime I passed my state inspection.

Interesting, let us know how the story develops.

I had the same code with my 2000 CRV, went to the dealer and paid $92 inspection fee. Did not go with $1050 replacement, but the "check light" came back.
In a meantime, I purchased ODBII reader/reseter for $27 on e-Bay, aftermarket converter "Estern Catalytic" and tried to replace the part. It was a hustle, to say the least, to remove the rusted rear bolts. Two of them broke. The converter looked fine - no visual sign of any issues. After I put the new converter the car behave strangely - like the exhaust was cloged/engine misfiring, the converter became red hot. After 4 more hours of removing the remains of the original bolts, removing the aftermarket converter I installed back the good old original. So far the car works fine, no check engine light. I'm sending back the aftermarket junk and will wait for a couple of weeks to see what happens.
If the light comes back on, I'll purchase another aftermarket unit -this time will go with Bosal, and will buy some generic O2 sensors. I'm getting pretty quick in installing this stuff. Kind of fun...

...and, oh, one more thing: the Auto Zone guy also suggested that if you ever take the cat converter off... BEFORE spending money on replacement: (1) shake it, (2) if you hear rattling it may have metal/rusted bits floating inside, and (3) if so, try to shake the bits out of one end or the other, and finally (4) put the old cat converter back on. It may be ok after all - just the rusty/metal bits may be the cause of fault indicator. Always remember to clear the check engine/p0420 code before hitting the road again...

BTW... now about 145 miles after my clean/new gas procedure and no fault indicator yet...

about 1300 miles since i used the fuel conditioner and two tankfulls of Sunoco 93 and no more check engine light (code 240 = catalytic converter problem). So I was very lucky: saved $1000+ on new dealer converter/oxy sensor and passed NJ state inspection!

Good advice, except what is a Usual Gas Conditioner?? STP like stuff?
Thanks!!!

Give it time.....it will recode