1998 voyager serivce engine light

own 1998 plymouth grand voyager. When pulling into the drive tonight I noticed the service engine light came and stayed on. I have no owners manuel to check. All I know is that at this time a year ago when this light came and stayed on---then went off---came back on again, I ended up replacing my transmission---was this a fluke??? I don't know. I just know that my service engine light has came back on----I really don't feel like replacing another transmission this year. Can anyone help me!!! With out owners manuel I have no clue what this light means!!!!
Just before light came on when backing out of parking space I notice my van was running a little rough and sluggish to go.

you can go to a local autozone or other auto part store and have them pull up any codes why your service engine light is on.