It means exactly what it says "Service Engine Soon"
I will give you a short list of SOME of the "Check Engine" or "Service Engine" items. NOTE that this post is Generic and NOT specific to your engine.
Oil life may turn on that light (If the oil life counter has not been reset even if the oil was changed, if he forgot to reset it..)
I have a problem with my car just now, and the code translates to a laundry list of things that includes "Loose gas cap".
Low oil pressure
Low fuel pressure
Restricted air flow
High/Low battery/System voltage
High temp Engine or transmission
Oxygen sensor wet
The short list of possible errors I have beside me (NOTE this is not a complete list) starts with P-101 and ends with P-1870
These are OBD II diagnostic codes.
Now; To find out.. Get yourself an OBD II error code reader (Mine is a very basic one that was not as expensive but most of the ones I see now are in the 70-700 range) READ THE MANUAL.. Plug it into the OBD II port and ... Read the code.