Challenge: how many combinations? (car immobilizer)

in my car i have a combination-lock immobilizer.

the combination lock is built like so:
[] [] [] []

four keys. each key however, holds more than just one digit:
[123] [45] [67] [890]

so a combination might be:
1234
2579
etc.

now, one might think that this can be used to reduce the number of times you have to hit every key when you brute-force the device, as the same keys would be hit for different digits.

some questions:
1. what is the minimum number of combination for brute-forcing the lock? how so?

2. the lock “locks up” for a few minutes (say, 3) after 3 failed attempts, how would this effect your method, if at all?

this is a rather easy one, but it may surprise you. i will post a follow-up once this one is solved to my satisfaction.

solutions are to be emailed to me directly rather than put in a comment. :)

gadi evron,
ge@beyondsecurity.com.

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  • sunshine

    I’d like to remind people to send the solution of their choice to me via email rather than in a comment. I don’t feel paranoid enough to moderate, I’ll just delete answers given here.

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  • noam

    As one of the guys that was able to change the code for this immobilizer without knowing the previous code, I can safely say don’t bother with calculating the number of combinations :)