Crank but no start after driving fine the day before

First you must check for fuel pressure and spark to see if one or both are missing. Also, listen for the hum of the fuel pump for one second when you turn on the ignition switch. If you hear that, you will have normal fuel pressure, but the pump may not resume running during cranking.

If you have a scanner that displays live data, look at the crankshaft position sensor and the camshaft position sensor to see if their signals are listed as missing or "present". Those sensors often do not set a diagnostic fault code just from cranking the engine. Sometimes they only set while a stalled engine is coasting to a stop.

First thing, try resetting security system. if that does not work check fuses under hood and then check fuel pressure with a gauge auto parts rent it. there is a tap on fuel rail for doing this see links.
https://www.2carpros.com/articles/how-to-reset-a-security-system
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

You do not need to run engine for scanning for codes just turn key on.

Per your question in a previous reply, if the engine is running, the cam and crank sensors are working, so there is no need to check them. It is only when spark and fuel pump / injector pulses are missing that you need to determine which signal is missing.

I must clarify that you can have a crank / no-start due to loss of fuel pressure, loss of spark, or most commonly, loss of both. If you find you have no spark, do not waste your time working in the fuel supply system, but, understand there is going to be fuel pressure because the pump will still run for one second when you turn on the ignition switch. You are not likely to have a separate spark-related problem, and a fuel pump-related problem, at the same time. Also, if you have a failed fuel pump, you can be pretty sure you are going to have spark yet.

It is easy to tell if you have no spark or you have no spark and no injector pulses by simply observing if there is a heavy gas smell at the tail pipe. No gas equals no injector pulses or no fuel pressure, and when you have either of those along with no spark, you know you need to look at what both systems have in common. That is both systems are turned on during engine rotation, (cranking or running), and the engine computer knows that by the signals it gets from the cam and crank sensors.

Since your truck is relatively new, (compared to what I drive), there is likely a main generator fuse that is bolted into the fuse box. That is because it has to pass a potentially really high current and simple plug-in terminals cannot handle that. Ford also used a smaller 15-amp fuse for the field current. That is a maximum of three amps, but that circuit also powers the built-in voltage regulator. It is not too uncommon for that 15-amp fuse to blow when the regulator shorts. People find the inoperative generator and replace that, along with its built-in regulator, but they are not aware of the blown fuse.

If there are no terminal for that fuse in the fuse box, that fuse is for an optional circuit that is not on your truck. If it is needed, and the terminal broke off, your battery will run down as you're driving, typically within an hour. We can discuss that if it becomes necessary.

The quick way to tell if the generator is working is the "Battery" warning light turns on when the ignition switch is turned on, then it turns off once the engine is running. You will see the headlights or interior lights dim when you stop the engine. Or, the best way is to measure the battery's voltage with the engine running. It must be between 13.75 and 14.75 volts. There can still be a problem with the generator, but when the voltage is within that acceptable range, that only means it is okay to perform the second half of the tests, and that requires a professional load tester.

From VAUGHANLEE

Okay upon checking the fuses I found the fuse box diagram for the 2003 Expedition labels the number nine fuse the alternator fuse. But on my expedition the number nine does not have a fuse it is an empty spot without any of the metal prong connectors for the fuse to plug into. It is as if it is a spare space. I do not understand. The diagram clearly reads that it is the alternator fuse. Is this right?

I think you might be breaking up the wrong tree in the fuse box, does the engine crank over? if so doe it have spark and fuel pressure, injector pulse?

Here is a guide to check the injectors and fuel pressure gauge, you might need to rent one from the parts store or get one from Amazon.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

and

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Please let us know what you find so it will help others.

Best, Ken