Ran out of gas in 2004 Silverado pickup. Won't start now.

Try unhooking the battery it does a sort of reset. And check fuses all fuses and relays

You can put new one and try fit.

oil sending unit replace

Bad gasoline

I doubt the problems are connected.
The check engine light could be anything including the loose gas cap.
But if that was the only problem it would not keep the truck from moving.
If it starts and runs, but won't go into gear, something has happened to the transmission or axle.
You may have to get it towed to a shop to find out what the trouble codes are in the computer.

Has the check engine light come on at all ?

Hi...sounds like you might need to replace your Distributor Magnetic Pickup !

Hope I helped!

It would be nice if you were to mention WHICH ENGINE your Silverado is equipped with...Knowing WHICH Silverado MODEL you have would also be nice...1500, 2500, 2500HD, 3500. etc.
If it is a gas engine, all you should have to do is to cycle the ignition key ON for about 5 seconds, then turn the ignition switch OFF and wait about 30 seconds, then repeat this about 3 times. This will allow the fuel pump prime to get the air out of the fuel lines. It should start after this is done.

If your truck is equipped with a diesel engine, the process is much different, let me know if this is the case, and I will post the fuel filter replacement instructions for the diesel.

Won't crank or won't start.

is it a desiel? or gas