Passive Anti-Theft System (PATS) - System Operation and Component Description: Pats

PATS

The PATS function is controlled by the BCM and the PCM.

When the START/STOP button is pressed, a voltage signal is sent to the BCM. When the BCM detects the START/STOP button is pressed, it begins the key initialization sequence by activating the PATS center antenna, the PATS rear antenna, the keyless entry rear antenna and both keyless entry door antennas. Each antenna transmits a low frequency signal with an approximate range of 1 m (3 ft). The passive key activates if it is within range of the antennas. The BCM is able to determine the passive key location (inside or outside the vehicle) based on the input from the antennas.

When the passive key activates, it sends the PATS identification code to the RTM via a high frequency signal. The RTM interprets the high frequency signal from the passive key and sends the information to the BCM over the LIN-based circuit.

If a valid programmed passive key is detected inside the vehicle, the BCM transitions the ignition out of off.

When the ignition transitions out of off and the modules initialize and the PCM sends a challenge request to the BCM. 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.

The PATS and the RKE system share operation of several components including the passive keys, the BCM and the RTM.

If a concern exists with any of these components, the PATS and the RKE system are both affected.

In the event of a no start (such as the batteries are depleted within the passive key), a valid programmed passive key is placed in the backup location to allow the vehicle to start. The PATS center antenna activates the transponder within passive key when the START/STOP button is pressed. The passive key transponder transmits the keycode which is read by the PATS center antenna and sent to the BCM.

NOTE: If available as a selection on the scan tool, the passive start feature is a programmable parameter and can be enabled/disabled. If the feature is disabled, the features to passively enter and start the vehicle are inoperative. To start the vehicle, the passive key must be placed in the backup starting location.

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

For information on ignition states, Refer to: Steering Wheel and Column Electrical Components - Overview .

PATS Parameter Identifications (PIDs)

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

BCMPID Chart

Acronym	Name	Description
KEYS_PROGMD	Number of ignition key codes supported	Displays the number of keys currently programmed into the BCM.
MIN_KEYS_RQD	Minimum number of keys required	Minimum number of programmed keys required. This PID always reads 2.

PCMPID Chart

Acronym	Name	Description
PATSENABL	Vehicle enable status	Indicates if the PATS allows the vehicle to be driven. Must read enabled for the vehicle to be driven.

No Key Detected Message

NOTE: Some brands/types of mobile phone or laptop computer chargers may cause interference that could lead to a PATS concern if the passive key is within close proximity of the charger. If a concern is observed, move the passive key away from the charger and attempt to turn the ignition on.

There are 2 scenarios in which the No Key Detected message displays in the message center.

The first is when the ignition is off, the START/STOP button is pressed and a valid programmed passive key is not detected inside the vehicle. If a component failure (such as a depleted passive key battery or RTM failure) is causing the No Key Detected message to display, the backup starting method can be used.

The second scenario is when the ignition is ON, the driver exits the vehicle with the programmed passive key and closes the door.

The BCM activates the center PATS antenna, the keyless entry rear antenna and both keyless entry door antennas to search the inside of the vehicle for a passive key any time a door or the luggage compartment lid is opened and then closed with the vehicle running and the first time each drive cycle the vehicle speed exceeds 15 km/h (9 mph). The No Key Detected message displays in the message center and the horn chirps twice when the ignition is on and a passive key is no longer detected inside the vehicle.

This strategy deters the passive key from being separated from a vehicle with the ignition ON. If a passive key is no longer in the vehicle, the ignition remains on and the vehicle continues to operate. When the START/STOP button is pressed to turn the ignition off, the ignition can be restarted without a passive key present inside the vehicle for approximately 20 seconds. After 20 seconds have elapsed, a passive key must be present to transition the ignition out of off.

Backup Starting

In the event the No Key Detected message displays, place a valid programmed passive key in the backup location to allow the vehicle to start. When the START/STOP button is pressed with a valid programmed passive key in the backup location, the center PATS antenna activates the passive key and the identification code is sent to the BCM. The passive key must be oriented correctly in the backup starting location.