DRFtstang

Yesterday i was installing the O/R x pipe and i dindnt like the sound of it so i took it out and installed the stock one back. Last night i took the car out to the street races, and the car ran exccelent. To day i went out with my family and the car started great ran great to the place we were going, but after eating when i got in the car to go home i didnt start, and the FailSafe Engine Mode came ON. I got in the car pluged the sct and the code P0421 came on( An oxygen sensor is not reading ) so my friend let's me borrow his O2 Green sensor wish is the only one that is On because the sct tune that Doug at Bamachips sent me had the blue ones turned off. Then I took out the (-) & (+) terminals for about 10 minutes turned the ignition on and there it is Fail SAfe engine mode. The car starts for about 5 seconds or it 2 and then turnes off itself. ALSO I NOTICED THAT EVERYTIME I PUT THE IGNITION ON THE TROTTLE BODY TRIES TO OPEN & CLOSE LIKE 4 TIMES. aNY HELP COMES GRATEFULL.