Starter runs continuously

Could be the relay stuck closed or the starters relay control driver inside pcm has failed closed. Drivers failing is very common. Usually they fail open but sometimes they do fail closed which would result in what your seeing. (A constant ON command to the starters relay.) Other then that your starter relay has a short to ground on 85 terminal or the starters relay has a short to 12V on 87 terminal.

Pulling the fuse interrupts the supply from relay to the starter so we can safely assume its on the back side of this fuse which should be a relay.

First check relay. If not relay check terminal 85 in fuse box for the starter relay to see if there is a constant ground signal If yes, Disconnect pcm. Now probe 85 terminal again to see if its still shorted to ground. If yes, find and repair If no, suspect the pcm.

If 85 signals are good (it should only show ground when cranking), Check 87 to see if its it has 12V If yes find and repair short, maybe suspect fuse box.

There are at least two conditions that can cause this. One being a defective starter where the starter solenoid contacts are closed so unswitched battery power is sent to the starter. You have eliminated this cause by pulling the fuse and shutting off the starter. That leaves the control circuit which goes through the starter relay. In some vehicles the same style of relay is used in more than one position. Check your fuse box or "power center" for a relay marked starter. Look for another relay with identical markings. Swap the relay and see if the starter spins. If it doesn't spin the relay is the problem. The car may not start depending on what the relay you removed controls. But you have isolated it down to being the relay.

If it was the small relay fuse and not a large solenoid fuse, then the small starter relay is welded closed. Replace it.