System Operation

Passive Anti-Theft System (PATS) - without Intelligent Access (IA)

System Operation

System Diagram





Network Message Chart

Module Network Input Messages - PCM (Powertrain Control Module)





Module Network Input Messages - BCM (Body Control Module)






Passive Anti-Theft System

The PATS (Passive Anti-Theft System) is controlled by the BCM (Body Control Module). There are 2 main checks that PATS (Passive Anti-Theft System) performs before allowing the engine to start. If either of these checks fail, PATS (Passive Anti-Theft System) does not allow the engine to start and STARTING SYSTEM FAULT is displayed in the message center. These 2 checks are the BCM (Body Control Module) verifying the PCM (Powertrain Control Module) identification to make sure it matches the PCM (Powertrain Control Module) identification stored in memory and to verify that a programmed key was used to turn the ignition to the RUN or START position.

The first check is initiated by the BCM (Body Control Module) waking up the PCM (Powertrain Control Module) by supplying voltage on the wakeup control circuit. The BCM (Body Control Module) only activates the wakeup circuit 5 times. After that the wakeup circuit remains off until the ignition is cycled to RUN. The BCM (Body Control Module) activates the wakeup control circuit when:
- the driver door is opened.
- a remote start request is received (if equipped with factory remote start).
- the brake pedal is pressed.
- a key is inserted into the ignition.
- or when the ignition is in the RUN or START position.

Once the PCM (Powertrain Control Module) is awake, the BCM (Body Control Module) sends the PCM (Powertrain Control Module) a challenge message over the HS-CAN (High Speed Controller Area Network). When the PCM (Powertrain Control Module) receives the challenge message, it generates a response and sends it back to the BCM (Body Control Module). If the response from the PCM (Powertrain Control Module) does not match the response in the BCM (Body Control Module) memory, this first check fails and the engine will not start.

Once the PCM (Powertrain Control Module) identification has been verified, PATS (Passive Anti-Theft System) performs the second check to make sure a programmed key is in the ignition. When the BCM (Body Control Module) determines the ignition has been turned to the RUN or START position, it generates a challenge message. It sends the challenge message to the PATS (Passive Anti-Theft System) 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 (Body Control Module) on the receive (RX) circuit. If the message received from the transceiver does not match a key stored in the BCM (Body Control Module) memory, the engine will not start.

If both the PCM (Powertrain Control Module) identification and key verification pass, PATS (Passive Anti-Theft System) is enabled and allows the engine to start. PATS (Passive Anti-Theft System) cannot disable or stall an engine that has already been started.

PATS (Passive Anti-Theft System) PIDs (Parameter Identifications)

In conjunction with DTCs (Diagnostic Trouble Codes), the PATS (Passive Anti-Theft System) PIDs (Parameter Identifications) are a useful tool when diagnosing PATS (Passive Anti-Theft System) concerns.

Module PID Chart






Unlimited Key Mode

PATS (Passive Anti-Theft System) contains a feature called unlimited key mode. This feature allows a customer to program more than 8 keys to their vehicle if they request it. Each vehicle in unlimited key mode is set up with a special unlimited transponder security key code. This allows all of the customer vehicles to share the same mechanically cut keys. For an individual customer, any randomly selected security key that has been previously mechanically cut and electronically programmed to the vehicle is acceptable. REFER to Unlimited Key Mode Programming Unlimited Key Mode Programming.