Boxster 986 keys stolen
 

My unused 18 year old, spare set of x2 986 Boxster keys have been stolen from the house and this means they could return and get the car, if it wasn't blocked in on my drive. I still have the other (main) key that was used most of the time. I guess the cost and time to replace all the keys, door lock and ignition barrel switch and get them reset with the ECU would be a lot even if they were second hand?
Temporarily, I was thinking of removing the fuel pump fuse, C4 30amp as I have been told by a specialist this renders the car undriveable quite quickly and even stops the engine from running! But would that do any damage or induce warning lights and fault codes? The other idea was to fit a wheel clamp on the car or a steering wheel lock as a deterrent. Any better ideas or thoughts would be a help...

In the long term, is it possible to buy a new (blank) spare key and get it cut to fit the door and ignition BUT also reprogram both keys and the existing ECU with a new, different code so that the original (stolen keys) will not open or start the car? But I realise that this still means the thief could still get in manually with the keys he has!

We had a break in a few years ago. Similarly the bastards took keys to all our vehicles along with much more. Homeowners insurance would not cover the cost of replacement keys and referred us to our auto insurance carrier.
The auto insurance would only cover the cost of replacement keys, but not rekeying or replacement of the actual locks and ignition. Amazingly I was told that "IF" the cars were later stolen they would be covered by my theft insurance!
So I removed the neg. battery cable on the cars that we did not drive daily (my Porsches and wife's SL Mercedes) as a temporary measure.
I ended up rekeying all the cars at my own expense...
Pulling fuses or the fuel pump relay sounds like a much simpler solution.

If they have the key bit and the transponder that fits to the car, they don't need the radio module to open the car and get away with it.

If they have a radio module that fits the car they can get in the car. If they are in the car and have enough time they can get away with it.

The only solution is to replace the whole locking system.

An alternative could be to install a tracking system and some kind of addidtional immobilizer, so you get an alarm on you smartphone when somebody is trying to manipulate or move the car.

But all this can't prevent that they try to get in the car and cause damage. So best is to also secure the house and the garage. But what if they follow you when you leave with the car. In the end it is complicated to prevent everything.

The immobilizer can be reprogrammed with a PIWIS or PST2 to no longer recognize the old key codes for wireless unlocking or starting the car. The mechanical door lock will still open, but that is it. If you buy a new key and have it programmed, any dealer or indie should be willing to do this little extra bit for nil or close. Justmake sure to take any "good" keys with you so they can tell what to deprogram.

Maybe a dog and a 9mm

Yes, and that is the problem. Because you can get into the car without making any noise. And if you can do that and have a little biz of time, the car is yours.

For now, put a negative battery shut off/disconnect on the car. It is easy and inexpensive. At least until you figure out a better solution.

This is similar to the situation that I have with my Spec Boxster that has no door windows and no mechanical steering lock.

Electrical protections are mostly useless. With the mechanical portion of the key, they can unlock the doors and unlock the steering allowing them to simply push the car away (and into a waiting trailer to drive off unseen).

Suggestions: block the car in by another car; use a heavy duty cable and lock run though the wheels and chassis to a permanent object; put the car on jack stands and store the wheels in a secure location; wheel clamp, steering wheel lock, etc.

Markus, the alarm still works. So if a stolen key is used to gain "silent" mechanical entry, it won't remain silent once the alarm goes off. The burglar having the mechanical key just saves him having to pull out his pocket knife and slice the convertible top to reach whatever valuables are left lying inside. But if the key "pill" is deactivated, he better have several undisturbed hours and a very complete tool kit if he expects to drive that car off, and a good explanation as to why he is hanging out of your car with the alarm going off the whole time. And in fact, if your trunks are electronically released (2001+), he won't be able to get in them either, short of a crowbar or knowing where the emergency release is located.
So maybe don't park it in remote airport parking with the family silver lying in plain sight on the passenger seat. But for most everyday purposes, the car is pretty safe with a functional alarm to deter burglars from the cockpit, and an engine immobilizer that is bloody hell to defeat quickly.
I would (did) get it reprogrammed to no longer recognize the stolen key, then forget about it.
BOL

Let me just concede that Markus and Todd are both right, and that a committed car thief could snatch your car in such circumstances and no doubt silence the alarm as well while they worked.
But around these parts, the typical junkie-needing-a-fix or young adult ner-do-well that breaks into your house looking for something to fence and maybe a car for a quick joy ride to the scene of their next crime, well lets just say it would be unusual for them to come back later with an accomplice, a trailer, and a winch.
Professional car thieves might do this, but they seldom target 18 yr old cars that are common enough to be worth little yet unique enough to be easily identifiable at a distance.
And if I am not mistaken, most if not all european cars came with a special alarm treat denied us North American customers, in the form of a standard shock/movement sensor as part of the alarm system. Again, not bulletproof protection, but one more hurdle for a thief.
I've got plenty to keep me up at night worrying, but the fact that some #%&@ stole one of my keys a few years ago is pretty well at the bottom of the list. But maybe your list is shorter. Hope no one messes with your Boxster -or your house- they should be called out in the law as an acceptable reason for justifiable homicide IMO.

I am curious so asking this question , if you disconnect the negative cable will you still be able to electronically open the frunk ? I'm thinking you need to open the trunk to activate/flip the disconnect switch .

Thank you all for the very interesting comments and ideas. It seems the real issue is preventing access to the car interior, as any thief who gets in and then cannot drive it will trash the interior - here in UK most dodgy guys carry knives but I guess a frustrated thief might just trash the exterior if stopped from getting in it?
Maybe replacing the door lock with a second hand one with a different key and keeping the original key for the ignition and having both keys recoded to activate or undo the electrical locking system? Although, this is a messy solution

Also on my car, the front and rear boot levers have remained locked on until the car is driven or the switch played with the light staying on.

If you are thinking about removing the seats to get to the immobilizer, I would think that just having the seat removed would be a bit of a deterrent (try to drive a Boxster w/o a seat ;) )...additionally, this would also address the comment of a frustrated thief destroying the interior...they still could, but at least your seats would be safe.

I also like the idea of running a cable though the wheels, but perhaps a big chain would be more effective...not that it would work any better, but it would be more obvious, and an obvious deterrent is better than a stealthy one. I'm thinking of the line from "Doctor Strangelove" regarding the Russians having a "doomsday device" but wanted to keep it secret.... :)

Depends. Mine has a small wire that connects to chassis ground to allow enough power to run accsessories, but won’t start the car. Or, move the frunk cable release to where it is accessible via the tow bolt access.