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there is no such thing as a code as you have mentioned, its all done internally and tech 1 can not see it. its just a bunch of random numbers matched bye the key head and bcm. the key codes in the bcm in security is the key cut code for cutting a stalk not the fob at all
Cheapest way out i know of is a $40 ebay keyfob and holden dealer $30 program
A new keyhead has to be programmed with the code to match the BCM or the car wont start.This number is available through holden,they use your VIN to access this number from TIS2WEB which then allows them to program a new key.I have my 6 digit security number that holden used to program my new keys.I just asked the guy could I have the piece of paper with the number he used.He just put this number into the Tech 1,put the new key with new keyhead in the ignition and it programed the keyhead.Theres two different codes.Theres the security code and the key code as well.I think the 4 digit key code is the one you mentioned that does the stalk.The other is for the key programming and whatnot.