Passive Anti-Theft System (PATS)

NOTE: The illuminated ring around the ignition lock cylinder is integral to the PATS transceiver and is controlled by the courtesy lamp system.

Refer to: Interior Lighting - System Operation and Component Description .

The PATS function is controlled by the BCM. There are 2 main checks the PATS performs before allowing the engine to start. These 2 checks are the BCM verifying that a programmed key was used to change the ignition to RUN or START and to verify the PCM identification to make sure it matches the PCM identification stored in memory.

When the BCM determines the ignition has been turned to RUN or START, it generates a challenge message. It sends the challenge message to the PATS transceiver on the transmit (TX) circuit. The transceiver in turn reads the key and generates a response message that is sent back to the BCM on the receive (RX) circuit. If the message received from the transceiver does not match a key stored in the BCM memory, the BCM prevents the engine from starting.

Once the BCM verifies a programmed key is in the ignition, the PATS performs the second check. The second check is initiated by the BCM waking up the PCM by supplying voltage on the wake-up control circuit. The BCM activates the wake-up control circuit when any of the following occur:

The driver door is opened.
A key is inserted into the ignition lock cylinder.
The ignition transitions to RUN or START.
A remote start request is received (if equipped with factory remote start).

Once the PCM is awake, the PCM sends the BCM a challenge message over the CAN. When the BCM receives the challenge message, it generates a response and sends it back to the PCM. If the response from the BCM does not match the response in the PCM memory, this check fails and the engine does not start.

If the PCM identification and key verification pass, the PATS allows the engine to start. The PATS cannot disable or stall an engine that has already been started.