Something like this is almost impossible to diagnose without looking at it. The light should blink if the engine harness is off due to no input from the sensors. It might be easier to diagnose once everything else is reconnected, however if something is wrong you might damage something else when you reconnect everything. Get a multimeter or at least a 12V tester and start checking wires. If possible, put the wiring back to OEM and check if the problem still exists.