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Old 10-02-2019, 06:43 PM   #10
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,146
 

2003 L-Series 3.0L Sedan
Default Re: Aura remote start

Almost every GM model has a combination factory alarm and immobilizer.The factory alarm system is basically the horns and flashing lights to get attention. GM has immobilizers under several names, Passlock and Passkey. Both systems disable at least one of three things that makes EFI systems run - injectors, fuel pump, ignition (spark). A factory theft deterrent system is more difficult for thieves to steal a vehicle when its part of electronics. In GMs case, the body control module has programming for either Passlock or Passkey and works with the ecm that runs the EFI system. When the Passlock sensors detect ignition lock cylinder rotation (Passlock) and a discrete signal from the ignition switch to the bcm, the bcm compares the two signals and sends either a go or no go signal to the ecm. The ecm receiving a go signal allows engine starting and running. A no go signal sent to the ecm tells the ecm to prevent EFI from operating. Passlock disables injector operation - without injectors operating, the engine will never run. The starter can try cranking the engine but disabled injectors prevents engine running. The same for Passkey security.

Both GM security systems will have an indicator on the speedometer or tachometer - a symbol of a car with a large padlock or 'SECURITY' flashing in yellow to alert the owner of a theft attempt. When security is armed, the security indicator blinks once every few seconds to serve as a warning that the vehicle has a theft deterrent system.

Do you see any security indicator when the ignition switch is OFF, car locked? Security is enabled when a remote is used to LOCK doors. GMs remote keyless operation does two things, LOCK doors and enable Passlock or Passkey, UNLOCK doors and disable Passlock or Passkey. Passlock uses a plain ignition key. Passkey uses a rfid chip embedded into the plastic key body. PKIII is stamped on the metal part of the key. The rfid chip is the same as ones inserted into pets for positive identification when a lost pet is found and a scanner is held near the insertion site. Whether pet or vehicle, the xmitter sends a low rf signal exciting the rfid chip. The rfid chip generates a discrete bar code signal and broadcast to the nearby xmitter/scanner for decoding. In vehicles the ignition key inserted into the ignition turns on the nearby xmitter/receiver and if the key xmits the correct code, the bcm sends a go signal to the ecm to allow engine startup. US passports also use this rfid chip.

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