2003 Dodge Grand Caravan wont start

im going to say an almost dead battery .the hum you hear might be the fuel pump.you never heard it before because the van normaly starts .so boost your van if it starts you may have to replace the altenator the guages, no worries many cars do that .thats a code needing erased and if you disconnect the battery that may go away.

battery cable ends. these vans were famous for it. if you have factory soldered ends you might want to consider changing them

Had a caravan that sat idle for a couple of months. When I put a battery in it and tried starting it the asd relay started clicking like a stopwatch and wouldn't stop until the battery was disconnected. Plugged in a code reader and it would start and run as long as it was plugged in, unplug the reader and it would die. Turned out to be corrosion on the secondary ground wire where it bolts onto the negative battery terminal.

i would check the alternator

Check the battery first. Just because the lights are on doesn't mean it has enough power to start the van. If you or the van has a volt meter, the battery should read at least 13-14 volts to be good. If the battery is good then the alternator is good and we move on to the starter solenoid. I'm sure it's one of these. Do the lights go off or very dim when you turn the key? If so then battery.

is the battery dead

clicking noise could be low voltage,starter relay, or soleniod. have these checked before anything else

Try checking relays in the fuse box under the hood. If all checks out ok, check timing belt/chain.

Make sure you have installed the battery correctly red cable on the (+) and black cable on the (-) side sounds like it may be reversed this wold cause instant battery drain.

The starter for one. Is it not turning over at all or you hear a clicking noise. did the motor just quit and will not restart. consider that the motor could be seized up but that's a last possibility.

Robert