service engine light

The computer in your car stores in its memory what it saw was wrong when it briefly turned on the Service Engine Soon Light it is interrogated using a scan tool through a 16 pin connector under the dash. I have seen O2 sensor problems, some crank angle sensor and occasional injector problems.

Fuel system cleaner will almost certainly not affect the check engine light coming on. It means there's a failure in your emission control system, and it'll most likely need to be properly diagnosed and fixed by a professional. RepairPal has a guide for what to look out for and what to do: http://repairpal.com/check-engine-light