The engine does not crank at all when the key is turned. What could be the cause?

An engine that does not crank at all when the key is turned is often indicative of an issue with the electrical system or starting mechanism. One possible cause is an open fuse, which means the electrical circuit that delivers power to the starting system is interrupted. If fuse #31 is specifically tied to the ignition or starting circuit, an open fuse would prevent the necessary voltage from reaching the starter motor, thus resulting in the engine not cranking.

While other options could potentially lead to starting problems, they would typically cause the engine to crank weakly or make clicking sounds rather than a complete failure to crank. For example, a dead battery usually leads to dim lights and would often allow for some attempt at cranking, although it might be significantly weak. Low engine oil typically does not affect cranking unless associated with serious engine conditions that prevent operation altogether, which is not common. A malfunctioning starter motor could also lead to issues, but it usually presents symptoms such as clicking sounds or grinding noises before failing completely.

Therefore, an open fuse is the most direct electrical issue that can entirely cut off power to the start system and prevent the engine from cranking at all.