2007 Scion tC Lighting Problems

I HAVE DRIVEN 1270 MILE SINCE MY LAST OIL CHANGE. MY OIL LIGHT DOESN'T COME ON AND STAY ON WHEN THE OIL IS LOW OR EMPTY. IT WILL GIVE A QUICK FLASH. WHEN I CHECKED IT TODAY, 1/27/17 IT WAS 2 1/2 QUARTS LOW. THE CAR ONLY HOLDS 3 QUARTS. WHEN I TOOK IT IN ABOUT 4 WEEKS AGO FOR ITS REGULAR CHANGE THERE WAS NO OIL IN IT AT ALL. I COULD HAVE BLOWN MY ENGINE BECAUSE I DIDN'T KNOW! THE LIGHT DOESN'T COME ON. IT HAS BEEN CHECKED FOR LEAKS AND THERE ARE NONE. IT HAS BEEN MADE CLEAR THAT I HAVE TO DO AN OIL CHANGE EVER 1200 MILES NOT THE NORMAL 3000. THIS ISSUE IS UNSAFE BECAUSE I CAN BE DRIVING AND WITHOUT WARNING BLOW MY ENGINE. *TR

AT APPROXIMATELY 56K MILES RADIO LIGHTING, TEMPERATURE CONTROL LIGHTS WENT OUT. THE ENGINE MAINTENANCE LIGHT STARTING COMING ON AT ABOUT 60K MILES AND AFTER HAVING THE CAR CHECKED IT WAS DETERMINED THAT THE FUEL/OXYGEN SENSOR WAS NOT OPERATING PROPERLY SO I HAD IT REPLACED. THE LIGHT WENT OFF FOR APPROXIMATELY 200MILES THEN CAME BACK ON. I TOOK IT TO TWO DIFFERENT MAINTENANCE PLACES AND IT WAS DETERMINED THE SERPENTINE BELT NEEDED TO BE REPLACED. I HAD IT REPLACED. THE MAINTENANCE PERSON DROVE THE CAR FOR A WEEK APPROXIMATELY 125 MILES. THE LIGHT WENT REMAINED OFF. I BROUGHT THE CAR HOME AND TWO DAYS LATER THE LIGHT WAS BACK ON AND IS STILL ON. I CALLED THE SCION HEADQUARTERS 1-866-707-2466 AND WAS TOLD THE ONLY THING I COULD DO WAS TAKE IT TO A DEALERSHIP. I WAS TOLD THE THREE PLACES I HAD TAKEN MY CAR TO WERE PROBABLY MISDIAGNOSING THE PROBLEM AND ONLY A TOYOTA DEALERSHIP COULD PROPERLY DIAGNOSE ANY ISSUES I HAD WITH MY CAR. I WOULD LIKE TO KNOW IF THIS IS THE CASE...WHY ARE SO MANY PLACES EQUIPPED WITH THESE COMPUTERS IF THEY ARE NOT WORKING PROPERLY????? *TR