After i had van serviced, check engine light came on

You can reset it by disconnectingt the negative(-) battery terminal. I'm afraid you'll probably have to find out the trouble code and fix the problem before it will stay off.
There are two different ways to do this, one of them should work on your vehicle.
With out turn the engine on turn the ignition key; On, Off, On, Off, On, Off, On at this point if you have a digital odometer the codes should show up there, If not the check engine light will blink out the codes. It will blink each digit three time then move on to the next. The first number should be 12 this means enging not running, the last number should be 55 which mean codes complete.
The other method generally used for older vehicles, you shouldn't need it but I'll expain just in case;
You should be able to short the 2 bottom right connections on the reader plug to activate the trouble code display then the display will work as I desribe earlier. Once you have the trouble code(s) I or one of the other expert here can tell you what it means and most likely how to fix it.

Go to any auto parts store and ask them to read the codes and if none
then ask to turn off the lite. if it comes back on in a few miles there is a problem and you need to fix it to keep light off.