System Operation: Pats

The PATS is controlled by the IPC. There are two main checks the PATS performs before allowing the vehicle to start. If either of these checks fail, the PATS does not allow the vehicle to start and the anti-theft indicator in the IPC flashes rapidly.

These two checks are to verify that a programmed key is used to turn the ignition to ON or START and the IPC verifying the PCM ID to make sure it matches the PCM ID stored in memory.

The first check is initiated when the ignition switch is turned to the ON or START position. Once the IPC determines the ignition has been turned to ON or START, it generates a challenge message. It sends this challenge message to the PATS transceiver on the transmit circuit. The transceiver in turn reads the key and generates a response message that is sent back to the IPC on the receive circuit. The engine does not start if the message received from the transceiver does not match a key stored in the IPC memory.

Once the IPC determines a programmed key is used to turn the ignition to ON or START, the IPC sends the PCM a challenge message over the HS-CAN. When the PCM receives the challenge message, it generates a response and sends it back to the IPC. The engine does not start if the response from the PCM does not match the response in the IPC memory.

If both the PCM identification and key verification pass, the PATS allows the vehicle to start. The PATS cannot disable or stall a vehicle that has already been activated.

PATS Parameter Identifications (PIDs) 

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

IPC PID Chart