KARR is the de-facto supported alarm system for Toyotas. I have one as well (2007 Toyota Yaris), but I stopped using it for the last 5-6 years because someone else's remote in the garage disarmed it. I always armed it and most of the time in the morning it was disarmed upon walking up to it. One day my GPS got stolen this way: I kept it in the glove box (not any more for sure!) and the thief only needed to open the door because the disarm procedure unlocks the driver side door with an actuator. So I thought I just won't arm it at all (although some other remotes could disarm it but no remote ever armed it other than mine).

Since then I moved to a new state, and recently there were two occasions when I found my window rolled down (it's a manual window and basically with some simple tools and force you can force it down). Fresno is the car theft capital now in the US. Fortunately since my GPS got stolen I literally don't have anything in the car, not even the registration nor the title. And having a stick shift is somewhat of a theft protection - dumb thieves mostly don't bother with it. I decided to use the alarm again, but in this new state and apartment complex yet again someone's remote disarms it - as I learned -, although less often (students live around here and their schedule is more hectic I guess, plus it's summer time).

I don't know what to do about this. These alarm systems supposed to use "jump code" technique and whatnot which theoretically shouldn't allow any other alarm other than the designated one to disarm it. But I know the phenomena exists: my ex boss's garage door was rolled up to one of the close neighbor's house alarm remotes (they had several, and only one of the rarely used ones rolled up my boss's garage door; it turned out accidentally one day when my boss saw it with his own eyes, before that he and his wife blamed each other). This was with one of the most expensive garage door system (Hormann, this was in the EU). Same thing: should not have ever happened theoretically but it did.

  1. How is it possible at all that other remote disarms my car? I've read about "jump code" system (which is kind of childish compared to a proper cryptographic system - I'm a software engineer also skilled in cryptography), it should not allow other remotes to interfere.

  2. How can I handle this? Should I just disconnect the driver side door's lock actuator so at least it won't unlock the door if it disarms? Or there's a better solution?

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