2000 Cadillac Escalade V8 All Wheel Drive Automatic 175000 miles

MY SERVICE ENGINE SOON LIGHT HAS COME ON. CAN YOU HELP ME TO DETERMINE WHAT MIGHT HAVE CAUSED IT TO COME? I KNOW MY OIL HAS NOT BEEN CHANGED IN AWHILE AND THE OIL CHANGE LIGHT DOES COME ON.

Can't determine from here why the service engine soon light came on. It needs to be checked with a code reader plugged in. Most auto parts stores and repair shops will test this for you (most at no charge) and be able to get an answer from the vehicles computer as to why the check engine light came on.