System Operation: Pats

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

The RFA module sends voltage 2 signals to the START/STOP push-button ignition switch. When the START/STOP button is pressed, the voltage signals are routed to ground, indicating a button press to the RFA module. When the RFA module detects the START/STOP button is pressed, it begins the key initialization sequence by activating the 3 PATS 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.

When the passive key activates, it sends an identification code to the Radio Frequency (RF) receiver via a high frequency signal. The Radio Frequency (RF) receiver interprets the high frequency signal from the passive key and sends the information to the RFA module over a LIN-based circuit.

If a programmed passive key is detected, the RFA module transitions the ignition out of off.

When the ignition transitions out of off and the modules initialize, the PCM sends a challenge request to the RFA module. The RFA module 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 passive entry system share operation of several components including the passive keys and the Radio Frequency (RF) receiver.

If there is a concern with any of these components, the PATS and the passive entry system may both be affected.

Backup Starting 

The vehicle can experience a PATS no start if a failure occurs with:

• the PATS front antenna.
• the PATS center antenna.
• the PATS rear antenna.
• the battery in the passive key.
• the Radio Frequency (RF) receiver.

In the event of one of these failures, place a programmed passive key in the backup location to allow the vehicle to start. The PATS transceiver activates the passive key when the START/STOP button is pressed.

The PATS transceiver is located in the steering column in the same location as a vehicle equipped without push-button start. If the vehicle does not start normally, place the passive key next to the steering column shroud and attempt to start the vehicle.

The RFA module 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 - System Operation and Component Description .

PATS Parameter Identifications (PIDs) 

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

RFA Module PID Chart 

Acronym	Name	Description
MASTERKEY	Master Key Present	Indicates if the key in the vehicle is a programmed key.
MIN_KEYS	Minimum number of keys required	Minimum number of programmed keys required. This PID always reads 2.
PATSENABL	PATS System Status - Enable Status	Indicates if PATS allows the vehicle to start.
PCM_ID	PCM ID Status Stored	Indicates if there is a PCM ID currently stored into the RFA module.
PCM_VFY	PCM Verify OK	Indicates if the PCM ID received by the RFA module matches the PCM ID stored in the RFA module memory.

PCM PID Chart 

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