There were some posts in the automotive forums recently asking about how to program a PassKey-III (PK3) replacement key. After a bit of research, I have the following to offer: Disclaimer: I have NOT personally tried these procedures, but have been told that they work on various GM vehicles. A wide variety of GM cars come with a passlock theft system feature that is meant to keep GM cars from being stolen. However, it isn't uncommon for GM car owners to experience glitches with their passlock system when trying to start their vehicle. When this occurs, you will see the security (Theft Sys) light being.

1. Gm Pass Key Bypass
2. How Does The First Generation Gm Pass Key System Work 2017

The Pass-Key, Pass-Key II, or VATS, as it's called in earlier GM

vehicles, uses a resistor mounted in the key blank to confirm that

the correct ignition key is being used to start the engine. Many

people call the resistor pellet a 'chip' due to the common

misconception that it is some sophisticated digital circuit to

identify the key to the car. Not quite. It is not a 'chip' of

silicon as is customarily used for integrated circuits, but merely

a block of carbon appropriately sized to have a desired electrical

resistance.

according to ehow.com there is a resistor built into the key and

if the value of the resistor in combination with the other ones in

your ignition do not match what is stored in your cars database the

system will reject the key.

Passkey III is not resistor-based. There is a rfid

(radio-frequency id) chip in the black plastic head of the key.

When the key is turned to start, the exciter coils in the lock

cylinder housing fire the id chip in the key, the theft-deterrent

module reads the rf signal and sends a password to the PCM - if the

key is recognised the PCM turns the starter and/or fuel pump on and

the car starts. If the key is unrecognised or the ignition cylinder

Gm Pass Key Bypass

is turned without a key inserted (no rfid communication to theft

deterrnet module) the PCM disables the starter and/or fuel

How Does The First Generation Gm Pass Key System Work 2017

pump.