Well, it happened again . . .
Van's battery (1.5 years old, and I top it off with an off-board charger every so often) is DEAD (2.4V) overnight. This happened 1.5 years ago as well when we replaced the battery just in case.
I have identified a common element in both cases: the van was parked with the doors locked for a day or longer without being driven. Then my wife used the remote to unlock doors to get something out of the van (first time, just the rear hatch, yesterday, the side door), did not start it or drive it, used the remote to lock the doors, and then the next day, battery completely dead (not 11.9V dead, so dead that no interior lights come on at all, not even dimly).
Whatever it is that is draining the battery, it is more than a few amps. A 1-2 amp draw will not bring a fully-charged battery down to almost zero volts overnight. So it's not a light bulb stuck on somewhere, I know that, and it wasn't the interior lights on either (we would have noticed those).
I am wondering if there is something wrong with the power locks or security system which is keeping something turned on when the 'lock' button is depressed on the key fob (like instead of just pulsing the power lock circuit, it keeps it on continuously).
It's maddening as it seriously reduces my confidence level in the vehicle. And what are my chances of finding the problem, when it has only happened twice in 1.5 years???
Anybody got any ideas? I have already purchased a datalogging Fluke multimeter for recording battery drain current for a similar problem in my 2001 Buick Lesabre (also has intermittent overnight battery-killing gremlin). Doesn't help much unless you can catch the problem in action, and then you have to pinpoint the exact source of the current drain. Arrrgggh!