System Operation: Pats

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

The PATS function is controlled by the BCM, ABS module the PCM and the SOBDMC (if equipped). There are 2 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.

The BCM verifying a programmed key when it is inserted into the ignition lock cylinder.
The PCM verifying the BCM identification to make sure it matches the identification stored in memory when the ignition state changes to RUN or START.

When the BCM determines a key is inserted into the ignition lock cylinder, it generates a challenge message. It sends the challenge message to the PATS transceiver over a LIN-based circuit. The transceiver reads the key and generates a response message to the BCM. If the message received from the PATS transceiver does not match a key stored in the BCM memory, the BCM does not respond to the PCM challenge request when the ignition transitions from OFF to ON.

The BCM activates the wake-up control circuit when a key is inserted into the ignition lock cylinder or a remote start request is received (if equipped with factory remote start).

The BCM wakes up the PCM by supplying voltage on the wake-up control circuit.

Once the PCM is awake the PCM sends the BCM a challenge message over the HS-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 data in the PCM memory, this check fails and the vehicle does not start.

When the ignition transitions from OFF to ON and the modules initialize, the PCM sends a target 1 challenge request, the SOBDMC sends a target 2 challenge request (if equipped), and the ABS module replies to a target 1 challenge request to the PCM. The BCM replies and if the correct identification is received, the PATS disables and allows the vehicle to start. If the PATS prevents the vehicle from starting, a DTC sets in one of the modules.

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

The BCM controls the ignition modes and, in conjunction with the PCM and ABS, controls the PATS.