What would happen to the engine if the ECM does not receive a speed/timing signal?

When the Engine Control Module (ECM) does not receive a speed/timing signal, it typically leads to a situation where the engine cranks but does not start. The speed/timing signal is crucial for the ECM to determine the position of the engine and to manage fuel injection and ignition timing appropriately. Without this signal, the ECM lacks the necessary information to optimize the engine's performance and cannot activate the fuel and ignition systems correctly. This disruption prevents the engine from starting altogether, leading to a condition where it will only crank without igniting.

The other options imply scenarios where the engine might run, either at a governed speed or idle speed, which is not possible without the essential speed/timing information that the ECM relies on to function properly.