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Immobiliser. How does it work?


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#1 Regulator

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Posted 16 October 2005 - 01:33 PM

Ok, u r probably going to think that this is random, but how does the engine immobiliser work? Does it change the code with the key eachtime the car is used, or does it stay static. Also, if it changes constantly and then, u use the spare key, how will that have the same code as the original key and the newly assigned engine immobiliser number. If that makes any sense???

#2 Lordz

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Posted 16 October 2005 - 08:53 PM

Basic way an imobiliser works is if it isnt disarmed the ignition,fuel or starter is taken out of the system(typically).
If its a factory fit imobiliser its virtually impos to bypass as most of the imobillisation is part of the ECU and the code is always the same as the transponder is in the key and the reciever around the barrel,most are recepticles but still in order to bypass it takes quite a bit of work,a typical way and imobiliser works is when yer open yer door it begins to search for the right code which will be on or in yer car key when its in ignition it reads it and closes all open circuits it has created,no the code cant keep changing cos yer spare key would stop working.

#3 5to1

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Posted 17 October 2005 - 03:30 PM

It can change, because the code can be dependant on the key.

Moreover, I believe the newer systems are based on Public/Private key algorithms. And so the system would have the key pair associated with each key.

#4 Chillihead

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Posted 18 October 2005 - 07:58 PM

[ QUOTE ]
It can change, because the code can be dependant on the key.

Moreover, I believe the newer systems are based on Public/Private key algorithms. And so the system would have the key pair associated with each key.

[/ QUOTE ]

Correct, the majority of alarm/immobilisor set ups utilise a rolling code, this is however, contrary to popular belief, not a random code, so each key will follow the same pattern, albeit with 1,000,000,000's of permutations.
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#5 DukeDesmo

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Posted 18 October 2005 - 08:57 PM

Mmmmm... I don't know about my Audi key but my last car (BMW 323) had an aftermarket Clifford alarm which claimed to use rolling codes, yet I had 2 remotes both of which would work (and according to the manual I could programme more), always wondered how 2 different remotes could generate the same 'random' code. /ubbthreads/images/graemlins/beerchug.gif
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