My Caravan has recently been worked on and.

The ECU or computer may need to be rebuilt. If it has a fault it should show up under a trouble code pull. Go to any Advance Auto or Auto Zone and they will pull the trouble codes for free. That is the first thing you should do. The codes will give you an indication if the ECU is working or not. If no codes come back. It may be a bad ECU. Hard to say. Most rebuilds only cost $300. Look on the internet or use the search engine on this site to find an ECU rebuilder who can put your ECU on a tester that will determine if it needs a rebuild.
It is a really tough call to make when an ECU is involved, a simple cycling by removing the positive battery cable for 15 minutes is a good rule of thumb to reset any ECU. Some have to be reset using special tools that only a dealership will have.
Get the trouble codes first, then disconnect the battery and see what happens. Then I reccomend sending your ECU to a rebuilder if the problem persists.