Here's what you should do:
1. Get the diagnostic trouble code (DTC): You'll need a OBDII code reader. These are inexpensive and readily available at auto parts stores. Plug it into the OBDII port (usually under the dashboard) and read the code(s). The code(s) will tell you *what* triggered the CEL.
2. Address the problem: Once you have the code(s), look up the meaning online (many free resources are available) or consult a repair manual for your specific van. This will help you identify the issue. This might be something simple (loose gas cap), or something more complex (a failing sensor or other mechanical issue). You may be able to fix it yourself (if you're mechanically inclined), or you may need to take it to a mechanic.
3. After repairs, clear the code: *Only* after you've repaired the problem that triggered the CEL, you can clear the code using your OBDII code reader. Most readers have a clear code function. The CEL should stay off if the repair was successful. If it comes back on, there's still a problem that needs addressing.
Do not simply reset the light without fixing the problem. This is a dangerous practice. The light is a warning system; ignoring it can lead to serious engine damage or even safety hazards.
