If your car is similar to the 850, the "Service Engine" light comes on periodically to remind you to change your oil, as well as other servicing. Nice trick to get you to take the car to a mechanic to turn off the light - but also a good idea for those who don't pay attention to servicing. Did you check your owner's manual as to the operation? On an 850 it comes on at both distance and time intervals. It stays on for the first few minutes of driving. On a '95, you can reset it yourself. On your car I think you need a computerized tool.