Engine position sensor opitions

EFI fundamentals>EFI components>Trigger inputs, question.

If your ECU loses track of engine rpm or position, and a different trigger system is needed, what are some other trigger inputs that can be used for engine position/ sync sensing? Thanks in advance.

It depends what the reason for the trigger input issue is in the first place. Often it's not the actual sensor that's the problem but rather the trigger disc or location of the trigger input.

For example often we will need to upgrade a trigger system that's located on the cam shaft to one that's driven off the crank to get improved consistency. In these situations hall, reluctor or optical pickups may still be used.

Is that also true for sequential fuel injection systems, and coil on pack equipped vehicles?

How does the ECU calculate the engine position, in the engine cycle?