verr1908

hi i live in england and have just got hold of a 305/700r4 tpi and harness cut out from a junk yard ,with the use of a book i have it fitted in a hot rod . only got the burn off relay and power relay ,so my fuel pump is running from the car wiring harness .my engine check light comes on after about 40 seconds of running the engine .when i set to give fault codes the ( 12 code )keeps going and does not stop untill igintion turned off also when in code set mode idle control make a buzzing sound any ideas