HI EVERYONE.NEED SOME EXPERTISE.I HAVE AN 04 MDX AND YESTURDAY I GASED UP.STATIONS HERE IN NY ONLY HAVE REGULAR THANKS TO HURRICANE SANDY. I HAVE ALWAYS USED HIGHTEST GAS.ABOUT 24HRS LATER MY CHECK ENGINE LIGHT CAME ON.CODE WAS PO420.CATALYST EFFICIENCY BEYOND THRESHOLD BANK 1.CALLED UP DEALER AND THEY TOLD ME IT CAN BE THE REGULAR GAS I PUT IN AND THAT THE MAIN COMPUTER SENSED IT.HE TOLD ME THAT IT SHOULD GO AWAY AFTER A COUPLE OF FILL UPS WITH HIGH TEST.HAS ANYONE EVER ENCOUNTERED THIS.ANY INPUT WOULD BE GREAT.THANK YOU.
Yes, it could be the fuel. It could also be that you didn't completely tighten the gas cap. So try doing that and see if the code goes away. It's a quick and easy thing to try, if you haven't tried it already.
Thanks guys for the reply.its an 04 with 145k.the check engine light did go off after about 2 days of driving.the dealer did tell me that the computer might adjust to the difference in fuel overtime.either way i am happy to know that it is not a bad catalytic converter i hear they are pretty pricey.i finally did find some premium fuel and filled up.as to the gas cap.that happened to me once before when i first owned it.i was told that the gas cap would have gave me an 440 code not a 420 code.lets hope that's the last i see of that check engine light for a long time.thanks once again.