Engine runs 20-30 minutes engine shuts off.

Question

Changed 3 times cam/crank shaft position sensor, changed fuel pump, fuel filter, intake air temperature sensor, manifold absolute sensor, throttle position sensor, engine fan relay, engine electrical fan, engine coolant temperature sensor, PCM and transmission overhauled vehicle towed in 4H. Check wiring on engine and transmission look ok. Disconnected engine coolant temperature sensor to see how long engine would run and keeping the PCM in the cold mode. Engine ran for 45 minutes, shut down and error code P0725 displayed on OBD II stating engine speed sensor system malfunction. Engine light illuminated for the first time. Not sure what to do next?

Answer 1

Monitor the ASD , (automatic shut down ) relay it supplies power to the 02 heater circuit , ignition coil and fuel injectors,. The best way is to monitor the voltage source , the ground source is given by the PCM,But for now do a visual to see if it is failing, Remove the cover of the ASD relay start the vehicle With key on engine off the relay should switch closed, With key on engine running the ASD should be switch closed, Run the engine if the engine stall and the ASD trips open it either from voltage source of a failed ASD.