Engine type, number of miles, what has been replaced in the last year or so, please.
This really helps us narrow it down.
I've had similar issues with my '96 GCV and the wife's '97 GCV. Both have 3.3lt engine.
On mine, the problem turned out to be the TPS (throttle position sensor).
Replaced it and it was like flipping a switch! Troubles be GONE!
On the Wife's van, it was the up-stream O2 sensor. It seemed like her van was starving for fuel, when actually it was flooding out.
Has it been really good on gas? Drinking gas like a pig?
Any other symptoms?
The "Key Dance" is.. "ON,OFF,ON,OFF,ON" within 5 or 10 seconds.
Count the check engine light flashes. The Chilton manual has the code key and I think it's also listed above as a sticky in this forum.
It's WAY better to use an OBD scanner tool.
Most auto parts stores are happy to scan your rig for free in hopes you'll buy the parts needed from them.
I'm an AutoZone guy. I like their rewards card program. I have $60 in credit racked up that will come in mighty handy when I need parts and I'm three days from payday.
As for the '05,... Can't help you there. I only fiddle with the old Caravans, sorry.