Had the same problem just now (July 2010) with my 2003 Grand Caravan with just over 90K on it -- some notes:
Do the reset with the trip button with the car off (not running) -- I learned this the hard way.
Expect to see something like "5 of 5.0" suddenly appear in the odometer display area -- when this appears, you can let go of the trip button.
Another message shows up -- some sort of E code -- and then the entire dashboard lights up like a Christm, er, "Holiday" tree (got to be PC) as it goes through internal diagnostics and the needles go back and forth -- and when it's done the speedometer needle is now above the pin.
Do the reset with the trip button with the car off (not running) -- I learned this the hard way.
Expect to see something like "5 of 5.0" suddenly appear in the odometer display area -- when this appears, you can let go of the trip button.
Another message shows up -- some sort of E code -- and then the entire dashboard lights up like a Christm, er, "Holiday" tree (got to be PC) as it goes through internal diagnostics and the needles go back and forth -- and when it's done the speedometer needle is now above the pin.