Keyless Entry System Description and Operation - Passive

WARNING: This page is about a different car, the 2007 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

The passive keyless entry allows you to enter a locked vehicle without pressing any button on the keyless entry transmitter. You must only have the transmitter with you. This passive system is also part of the vehicle starting system. It allows you to start and run the vehicle having only the transmitter as your key. The passive entry and starting system use low frequency antennas in 5 different areas on the vehicle to determine the location of the key fob to the vehicle. When passively opening a locked door, or a rear compartment lid, you must have a programed key fob with you in your pocket, purse, or briefcase. As a customer opens the door handle or rear compartment open pad, the low frequency antenna sends out a challenge to the keyless entry transmitter. The transmitter must be in a one meter range of the door or rear compartment lid that the customer is opening in order to receive the challenge. If the challenge from the low frequency antenna is met, the transmitter will respond, allowing the door to be unlocked and opened. Starting the vehicle also works in the same manner. The key fob must be within the passenger compartment of the vehicle when the Start/ACC/OFF button is pressed. The low frequency antenna sends a challenge to the transmitter and if the challenge is met, the transmitter will respond to the remote control door lock receiver (RCDLR). The RCDLR will then send out a fuel enable password to the engine control module (ECM). As long as all security requirements are met, and the ECM receives the password over the serial data line, the engine will start and run. A low transmitter battery or radio frequency (RF) interference from aftermarket devices, such as 2-way radios, power inverters, computers, etc., may cause a system malfunction. High RF traffic areas, such as gas stations that use pay-at-the-pump RF transponders, may also cause interference that could lead to a malfunction.

The passive keyless entry has the following components:

The keyless entry transmitters (up to 4 total)
The RCDLR
The LH door handle antenna, located within the LH front exterior door handle
The RH door handle antenna, located within the RH front exterior door handle
The console antenna, located in the passenger area, within the center console
The headliner antenna, located in the passenger area, beneath the headliner
The trunk antenna, located in the rear compartment area near the rear compartment lid latch
The console active antenna, located inside the passenger compartment, within the center console