How to diagnosis check engine light???

I have a 1994 Plymouth Voyager, 3.0ltr engine, auto trans. I went shopping came out to start my van and the check engine light stayed lit. The oil level is right where it should be, engine runs fine with no lack of power. Transmission shifts flawlessly. Again no overheating, no batt electrical problems.... I don't believe that this van is OBDII compatable. So what are some general causes for this light to come on?

van should be obd 1 cycle key 3 time red light on off on off onkepp on will tell code or o2

Translated:
Cycle the key from off to on (not start) three times leaving it on. Now count the flashes of the check engine/service engine light. The flashes represent a fail code. Code 21 would be flash, flash, pause, flash. Multiple codes are seperated by a longer pause. All are two digit codes. Should finish with a code 55. Try it and come back here with any codes you see.

If you have absoulutely no other symptoms you likely have an EVAP system fault. Tighten your gas cap.

this is all helpful except with todays market you should be able to take it to any schucks, autozone, advance autoparts and get the check engine light read for free.

if you still decide to do this i beleive the first couple of blinks are not an actual code yet. (rusty memory since the last time i did this though)