A person at my house continually moves my 2002 Ford Explorer from the driveway to the street without permission. The key is shared and must remain easily accessible. Personal issues aside, is there a way we can disable my truck so he can't move it, by removing a plug or cap to disable our vehicle like in the movies? What would be a few options?
If your friend is moving your vehicle without your consent and does so deliberately your friend is committing a crime. Vehicle theft. If you are asleep when this happens then consent was not given. I would suggest that you have a police officer have a long discussion with this individual about this. If this individual when moving your vehicle hits another vehicle and damages it. Since you are the owner of the vehicle you are responsible and your insurance rates will go up. As for disabling start looking into installing a kill switch . Also if you get parking tickets as a result....get him to pay for them.
I'll make it very simple for you, Dave.
Just remove the relay highlighted, in yellow, from the diagram above.
This goes to the starter.
Remove the publicly available key.
Make one copy of the key for each person or household who needs to be able to move the car. Give a key to each person and have them sign an agreement that they will not loan their key to anyone else.
If the individual is still able to move the car, he probably made an unauthorized copy, in which case you should contact the police.
I don't know what the cost of a parking ticket is in your area, but here I could make 30 copies of a key for less than one ticket.
As stated in other answers, you really need to get your new housemate to start listening to you. If he doesn't respect your property, do you really want him living with you?
With regards to the vehicle, your simplest solution is unplugging something on the ignition side. Historically, you could unplug the king lead (from the coil to the distributor) but as yours is likely on an electronic ignition system, I'd suggest unplugging the plug in the side of the coil pack or the sender unit for the inductive pickup that detects RPM. I'm not 100% sure on your vehicle but I'd guess it would be screwed into the bell-housing taking a feed from the flywheel.
With these unplugged, the engine will crank but not start. The problem here is, it's akin to hiding your keys because it means that you would need to know how to start the vehicle.
Remove fuse #26 (Brake-shift interlock) and the starter relay. This will prevent the "friend" from starting the car, and will also prevent the "friend" from simply putting it in neutral and pushing it (The Brake-Shift interlock fuse being removed will prevent the shifter from being moved out of "Park"). Most people haven't got the slightest clue about fuse boxes in cars, so it should work fine.
Hide the keys in a different non-obvious place.
Tell all your friends the new place where the keys go, except for the one you don't want to move the car.
Don't disable the vehicle. Put up a set of dummy keys, which you can get from any junkyard with a similar-year Ford, it doesn't even have to be an Explorer. The real keys you could hide somewhere, and inform the authorized drivers where they are.
Note that keys with plastic fobs may be damaged by applying too much force when trying to turn them in the external locks (door lock, hood lock). This may require a locksmith to retrieve the key blade from the lock. Thank you to Steve Matthews and Numair Aidroos for bringing this up in the comments.
As was said install a kill switch. This was originally relatively simple on older cars : fit a switch into the supply to the coil. However, you may find that a switch into the supply to the fuel pump would work - but the residual pressure may still allow him sufficient time to move the car. You will need to check, it will depend on the time between when your car was parked and when he tries to move it
My question, is there a way we can disable my truck so he can't move it onto a no parking zone by removing a plug or cap to disable our vehicle like in the movies?
The wire that they disconnect in the movies goes to the coil plug in a distributor cap like this:
The wires from the outer plugs go to the spark plugs. The central one brings the power in for all of them. So removing the central wire will disable the vehicle.
They also might remove the distributor cap entirely. Or they might unbolt it and remove the rotor from inside so that the spark doesn't travel from the coil wire to the spark plug wires. Any of those involve unbolting the cap, which is more work than I'd want to do in this situation.
The 2002 Ford Explorer does not have that kind of distributor though. It has an integrated ignition coil instead:
That video shows how to remove and replace the ignition coil. It's not something that you'd do quickly. It's a non-permanent way to disable a vehicle that you may be able to do without entering the vehicle (if you can release the hood). A simpler method would be to unplug the six wires, but it's easy to put them back in the wrong order. That can cause the engine to run incorrectly. Unplugging some but not all the wires can allow the engine to run just well enough to reach a no parking zone but not well enough to drive. Pretty much the opposite of what you want.
This is why another answer is recommending that you remove the starter relay instead. That takes seconds to remove and replace once you know where it is. If the orientation is not obvious, you can draw on the fuse box and relay with a marker to make it obvious which corner goes where.
The starter relay won't allow the starter to engage at all, so less chance of running down the battery, ruining the starter, or flooding the engine trying to start the vehicle. The distribution just keeps the spark plugs from firing. The starter will happily grind away.
A kill switch could also work. But I wouldn't recommend installing it yourself unless you plan on working on the car yourself in general. It's a mechanical (electrical) change. Take the car to a mechanic or security system installer to get a kill switch installed. Doing it incorrectly may not actually stop the car from starting or it may keep the car from starting more permanently than you want. You need both off and on to work.