[37mechatech]

i have a 2000 EX with about 98000 miles, and get bugged by the po420 code also. it seems to me that it comes on from bad gas and/or mainly lower octane with ethanol. heres why, i live in north texas were they didn't start putting ethanol in the gas here until last year. we never had an issue here. but before that 2 summers ago is when the cel came on first time and got the po420 code, we were at my parents in iowa, where they have had ethanol gas for years, now you have a choice there to buy the 'gasahol' it is the mid octane and always cheaper than 87 octane, plus it supports the farmers supposedly, anyway after buying this gas, on comes the light and to autozone i go to check codes and we got po420. since this has happened every time we would go back home and i mean every single time( twice a year, once in summer and thanksgiving), and i would buy the lower octane gas, the cel comes on. like clockwork.

Back to texas: once we returned to texas no more cel.
until last year when they all switched to ethanol blends, now i buy only 93 octane and the light stays out. until my wife puts in 87octane.(cause its cheaper)

so now when the light comes on i run whatever gas she has put in down to empty, go fill up with 93 octane and reset the light. and it stays off.

this is just my experience with this van, ethanol, and po420 code.