Ok, great. I think the reason your question sat so long without a response, is because the Service Engine Soon Light "is" in fact, the same as the Check Engine Light for this vehicle. If you turn your ignition key on and look at the dash, you should notice there is no Check Engine Light (the little shape of an engine) unless this is a Canada build. If this is the case, like i say, the Service Engine is the Check Engine light and if this light is on constantly, there "is" a problem and there "should" be "P-Codes" stored. If there are no drivability or performance issues, then more than likely, the problem lies in the EVAP (emissions control/recovery) System, as a fault here will not effect engine performance. Very commonly, this could be a faulty, loose or missing fuel cap or even putting fuel in while the vehicle is running can set the light. Check the underside of the fuel cap for any cracks or signs of defects that may keep the cap from sealing correctly. If there are any doubts about the inspection of the cap, replace it. Keep in mind, you will need a cap that meets OE Specs. Those "universal" or "locking" fuel caps sold at after market parts stores do not meet OE specs, and will not seal the system correctly. Check the top of the fuel filler neck for any signs of damage or debris. Check under the vehicle, around the rear areas of the vehicle, looking for any vacuum lines that have dry-rot cracks, holes or loose/missing connections. If these all check out, then the best thing to do at this point is to have the Diagnostic Trouble Codes (aka "p-codes") read from the on-board computer. These p-codes are what is used as a "starting point" for the diagnosis and will tell which part/sensor, in which system, has the fault. If a scan was done and no codes were found, it could be due to an older model scan-tool. I'd strongly recommend having the codes read again. You can have these p-codes read FREE (except in California) at any local "big chain" part store (ie. AutoZone, PepBoys, Advanced, etc).