Passive Anti-Theft System (PATS)

WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

The PATS function is controlled by the BCM and the RFA module.

When the START/STOP button is pressed, the RFA module initiates the key initialization sequence by activating the 3 interior PATS antennas. Each PATS antenna transmits a low frequency signal approximately 1 m (3 ft) radius of each antenna. If a passive key is within range of the 3 interior PATS antennas, the passive key activates.

When the passive key activates, it sends the PATS identification code to the TPM module via a high frequency signal. The TPM module interprets the high frequency signal from the passive key and sends the information to the RFA module over a LIN -based circuit. If the RFA module determines that a valid programmed passive key is inside the vehicle, it communicates this information to the BCM and the ignition transitions out of OFF.

When the ignition transitions out of OFF and the modules initialize, the RFA module, BCM, and the PCM exchange their identifications. If each of the modules receive the correct identification from each other, the PATS disables and allows the vehicle to start. If the PATS prevents the vehicle from starting, Starting System Fault displays in the message center and a DTC is stored in one of the 3 modules.

The PATS and the RKE system share the operation of several components including the passive key and the TPM module. If there is a concern with either of these components, the PATS and the RKE system are both affected. REFER to Handles, Locks, Latches and Entry Systems for information on the RKE and passive entry features.

NOTE: The passive entry/passive start feature is a programmable parameter and can be enabled/disabled with a diagnostic scan tool. If the feature is disabled, the passive entry feature to enter the vehicle and passive starting are inoperative. To start the vehicle, the passive key must be placed in the backup starting location.

The RFA module and the BCM control the ignition modes and, in conjunction with the PCM, control the starting system.

PATS PIDs

In conjunction with DTCs, the PATS PIDs are a useful tool when diagnosing PATS concerns.

BCM Module PID Chart

Acronym	Name	Description
PCM_ID	PCM ID Status Stored	Indicates if there is a PCM identification currently stored in the BCM. Must read stored for the engine to start.
PCM_VERIFY	PCM Verify OK	Indicates if the module identification check between the BCM and the PCM passes. Must read yes for the engine to start.
START_ENABLD	Vehicle Enable Status	Indicates if PATS allows the engine to start. Must read enabled for the engine to start.

RFA Module PID Chart

NOTE: The RFA module PATS PIDs do not actively display their current state. They only display the correct state when the ignition is turned to the RUN mode.

Acronym	Name	Description
BCM_ID	BCM ID Status Stored	Indicates if there is a BCM identification currently stored in the RFA module. Must read stored for the engine to start.
BCM_VFY	BCM Verify OK	Indicates if the module identification check between the BCM and the RFA module passes. Must read yes for the engine to start.
MASTERKEY	Master Key Present	Indicates if the RFA module detects a valid programmed passive key in the vehicle. Must read stored for the engine to start.
MIN_KEYS	Minimum Number Of Keys Required	Minimum number of programmed keys required. This PID always reads 2.
N_KEYCODE	Number Of Programmed Keys	Number of keys currently programmed into the RFA module.
PATSENABL	PATS System Status - Enable Status	Indicates if PATS will allow the engine to start. Must read enabled for the engine to start.

Backup Starting

NOTE: There are certain areas within the vehicle where the passive key may not be detected and the message center displays No Key Detected. If the passive key is in the far outside edges of the interior (such as in a door map pocket or above a sun visor), it may not be detected. Move the passive key to a different location and try to start the vehicle again.

The vehicle can experience a PATS no start if there is a failure of any PATS antenna, the battery in the passive key, or the TPM module. If this occurs, the No Key Detected message displays in the message center when the START/STOP button is pressed.

However, in the event of one of these failures, the passive key can be placed in the backup starting location to allow the vehicle to start. The passive key must be oriented correctly in the backup starting location. If a valid programmed passive key is in the backup starting location when the backup transceiver activates, the passive key identification code is sent to the RFA module.

Passive Key Backup Starting Location (Expedition)

Courtesy of FORD MOTOR COMPANY

Passive Key Backup Starting Location (Navigator)

Courtesy of FORD MOTOR COMPANY

No Key Detected Message

NOTE: Some brands/types of mobile phone or laptop computer chargers may cause interference that could lead to a PATS no-start 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 start the vehicle.

The No Key Detected message displays in the message center when:

the START/STOP button is pressed with the ignition OFF and a valid programmed passive key is not detected inside the vehicle.
the engine has been started or the ignition is in RUN and a passive key is no longer detected inside the vehicle.

The RFA module activates all the PATS antennas to search the inside of the vehicle for a passive key every time a door or liftgate is opened and then closed. This strategy aids to prevent the passive key from being separated from an already running vehicle. If a passive key is no longer detected in the vehicle, the vehicle continues to run. If the START/STOP button is pressed to turn the vehicle off, the engine can be restarted without a passive key present inside the vehicle for approximately 20 seconds. During that time, Restart now or key is needed displays in the message center. After 20 seconds have elapsed, a passive key must be present to start the vehicle or transition the ignition out of off.

No Key Detected Message (enhanced, if equipped)

NOTE: To determine if vehicle is equipped with the enhanced No Key Detected and Automatic Engine Idle Shutdown features, access Message Center>Settings>Vehicle using the message center controls. If "Auto Engine Off" is listed in settings, the vehicle is equipped with the enhanced No Key Detected and Automatic Engine Idle Shutdown features.

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 dead passive key battery) is causing the No Key Detected message to display, the backup starting method can be used.

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

The RFA module activates all 3 PATS antennas to search the inside of the vehicle for a passive key any time a door or the liftgate is opened and then closed with the vehicle running. The Key outside car 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 an already running vehicle. If the 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 10 seconds. After 10 seconds have elapsed, a valid programmed passive key must be present to transition the ignition out of off. If the driver door is opened during the 10-second countdown, a valid programmed passive key is needed to transition the ignition out of off.

Automatic Engine Idle Shutdown (if equipped)

NOTE: To determine if vehicle is equipped with the enhanced No Key Detected and Automatic Engine Idle Shutdown features, go into Message Center>Settings>Vehicle. If "Auto Engine Off" is listed in settings, the vehicle is equipped with the enhanced No Key Detected and Automatic Engine Idle Shutdown features.

The automatic engine idle shutdown feature monitors the state of the vehicle to determine when the engine is powered with no user interaction for an extended period of time. When this condition is detected, a message displays in the message center to inform the operator a vehicle shutdown is imminent. This includes shutting down the engine and turning the ignition off. When the shutdown occurs, press the brake pedal and the START/STOP button to restart the vehicle.

The conditions required to begin the automatic engine idle shutdown feature are:

engine running
brake pedal not applied
accelerator pedal not pressed
remote start not active
transmission in P (park) or N (neutral)
diagnostic scan tool not connected to the vehicle

Once these conditions are met, a time-out starts. When the time-out period ends and none of the listed conditions changed, the automatic engine idle shutdown event occurs.