GM Passkey III didn't require programing?

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So I lost the master key for my Envoy, so I got a new fob and coded key from the dealer. They asked me to come back tomorrow for programming, so I figured I'd do it myself. I put the new uncoded key in the ignition and turned it on - five seconds later the security light went off. I cranked the engine and it fired right up! I tried the 2nd memory key and it fired right up. Am I missing something here?
 
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Maybe someone put in a remote starter and it has a bypass module you don't know about. Did you get it new?
 

Falcon_LS

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Trav - same thing. shrug I bought it off the original owner who never changed/added anything. Based on what I've read, it appears I have a Pass-Lock system, which to my understanding is different than Pass-Key. To my understanding, there is no chip in the key - which explains why it cost $10 for a Genuine GM key vs. $30 for my Ford PATS key - the key is just used to make contact between the tip and the base of the ignition cylinder. The resistor is apparently located in the ignition cylinder itself. Maybe that explains why.
 
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Passlock just checks to make sure there is a key in the cylinder, passkey III has a transponder chip in the head of the key and requires programming. Is there any marking on the blade of the key such as PK3 or a circle with a + in the center?
 
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Originally Posted By: Falcon_LS
the key is just used to make contact between the tip and the base of the ignition cylinder. The resistor is apparently located in the ignition cylinder itself. Maybe that explains why.
So what exactly is this system supposed to prevent? Hot wiring can still be done - just put any old key in there....
 
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Hot wiring will not work on Passkey systems since there are Hall effect sensors in the ignition lock cylinder and the BCM must see the pattern generated when the ignition key is turned normally, else the BCM does not enable fuel.
 
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^ yup that. Deliberately confusing terminology on GMs part. But, they still get credit for putting passlock on the cheaper cars-- it still deters theft.
 
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Originally Posted By: George7941
Hot wiring will not work on Passkey systems since there are Hall effect sensors in the ignition lock cylinder and the BCM must see the pattern generated when the ignition key is turned normally, else the BCM does not enable fuel.
That makes better sense. Thanks.
 
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