2000 Dodge Caravan starter will not engage.

More involved then just a few thing's like other guy posted . The ignition switch is not a direct connection to the starter solenoid S terminal . Input to a computer , BCM - body control module , PCM - engine computer , TIPM - totally integrated power module etc... one of these modules (computers) energizes the starter relay sending battery voltage to the starter solenoid there by engauging the starter to spin the engine around. The starter relay contacts could be sticking .

have you checked the ignition switch thats on the steering column shaft, when you turn the key it moves a rod that moves positions on the switch.

No. Starter relay may also be known as the "solenoid". It works the starter motor.
Ignition system is a different system, and may not even have a relay, depending on your car.

Check ground wires on frame

need to check immobilizer unit device that will open the supply power to relay and start engine check up all circuit line who involves key switch and device

1 Inspect Battery Battery Discharged or Faulty. 2 Inspect Battery Cable Corroded, Broken, Shorted or Poorly Connected Battery Cable. 3 Inspect Distributor Cap Distributor Cap Cracked or Burned. 3 Inspect Fuel Filter Clogged or Dirty Fuel Filter. 5 Inspect Coil - Ignition Faulty Ignition Coil. 6 Inspect Wireset Worn, Damaged or Faulty Spark Plug Wire(s). 7 Inspect Spark Plug Incorrectly Gapped or Fouled Spark Plug(s). 8 Inspect Starter Starter Motor Faulty. 9 Inspect Fuel Pump Low Fuel Pressure. 10 Inspect Solenoid Switch Faulty Starter Solenoid Switch. 11 Inspect Relay - Fuel Pumpat Faulty Fuel Pump Relay. 12 Inspect Fuel Injector Pressure Regulator Faulty Fuel Injector Pressure Regulator. 13 Inspect Ignition Switch Improperly Connected or Faulty Ignition Switch. 14 Inspect Starter Drive Faulty Starter Drive. 15 Inspect Fuel Injector Dirty or Worn Fuel Injectors. 16 Inspect Fuel Pump Strainer Clogged or Dirty Fuel Pump Strainerat. 17 Inspect Engine Control Computer Incorrect Operating Information Being Delivered and Sent From The EEC. 18 Inspect Fuel Tank Fuel Tank Empty. 19 Inspect Carburetor Carburetor Flooded or Faulty Choke. 20 Inspect Distributor Worn, Loose, or Incorrectly Installed Distributor.

1. Check the Battery Terminal Post connections. Use a Battery Brush to clean (both the terminal post as well as the connecting rings) and make sure they are tight. If one is already loose dirty (not shiny metal) then it could cause intermitten non-starts.
2. Check the Starter Relay located in the IPM (fuse box) located in the engine compartment. The cover has the what relay is what. Relays that are the same can be switched and the functions checked. For example: the Rear Blower Relay is (should be the same as the Starter Relay. If the Rear Blower works (all the time) switch the Rear Blower Relay and Starter Relay. Check the Rear Blower several times (on and off). Check the Starter several times (on and off). If the Rear Blower works only intermittently and the Starter works all the time now, replace the bad relay. Don't switch back until you obtain a new relay.
3. I could also be the connections to the Starter Solenoid that have become loose or corroded.
4. It could also be the Starter Solenoid or the Starter Motor. If it is the Solenoid: with a partner-short jump (with a short-well insulated wire) the positive connection from the solenoid (small cylindrical body) to the starter body (large cylindrical body while your part turns the ignition to start. If it starts right-up, then the solenoid is bad.
5. You cannot (normaly) replace just the solenoid. Purchase a new or remanufactured Starter (which comes complete with the Solenoid) and replace the old Starter.
Good Luck and let me know if this worked or if you have additional information to clarify or need additional information.

Below are possible causes for your issue

1. Ignition switch is failing
2. Starter relay is failing
3. Battery connections are bad
4. Battery has reached end of useful life
5. Stater is bad

I'm curious, does this vehicle have an alarm/remote starter? If so I expect the installer didn't wire it correctly ... it was an all too frequent issue, with inexperienced installers we had .... I would first suspect any add-on device first (if any) ... In answer to your question ... I know it does have a relay (Starter solenoid is a relay and built onto the starter) As far as it being a relay or the IGN switch ... I'm skeptical.

resistor.............tell the mehanic