Principles of Operation
Anti-Theft - Intelligent Access (IA)
Principles of Operation
NOTE: Replacement of the backup transceiver, the Remote Functions Receiver (RFR) module, or any of the Intelligent Access (IA) passive start antennas does not require the IA keys to be programmed into the Remote Function Actuator (RFA) module again.
NOTE: When using the Integrated Diagnostic System (IDS), the RFA module and the PCM parameters are reset at the same time.
NOTE: Make sure any aftermarket remote start systems have been removed from the vehicle before any Passive Anti-Theft System (PATS)-related no-start concerns are investigated.
NOTE: A minimum of 2 IA keys must be programmed into the RFA module before the vehicle can start.
NOTE: If the RFA module or the PCM is being replaced (or both), the parameters must be reset in both modules or the vehicle experiences a PATS no-start. Refer to Passive Anti-Theft System (PATS) Parameter Reset - Intelligent Access (IA) With Intelligent Access (IA).
NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).
Anti-Theft Indicator
PATS flashes the anti-theft indicator every 2 seconds when the ignition is in the OFF mode to act as a visual theft deterrent. Refer to Instrument Panel, Gauges and Warning Indicators for information on the anti-theft indicator.
PATS is active only for a few seconds when the vehicle is starting. It is not a PATS concern if the vehicle stalls after it has been running for a minimum of 3 seconds. PATS cannot disable a running vehicle.
Intelligent Access (IA)
NOTE: A maximum of 4 IA keys can be programmed into the RFA module.
NOTE: The IA key must be inside of the vehicle in order to be used for starting the vehicle. There are a few areas within the vehicle that are out of reach of the 3 interior vehicle passive start antennas and can precipitate a PATS no-start if the IA key is located in these areas:
- Far outside edges of the visors (between the visors and the headliner)
- Far outside edges of the package tray
- Far outside edges of the bottom of the windshield (interior side of the windshield)
- Far corners of the rear seat
- Inside the overhead console
If the IA key is located in one of these areas and there is a no-start condition, move the IA key out of the area and attempt to start the vehicle.
NOTE: Some brands/types of mobile phone or laptop computer chargers may cause interference that could lead to a PATS no-start if the IA key is within a few inches of the charger. If a concern is observed, move the IA key away from the charger and attempt to start the vehicle.
NOTE: If the battery in the IA key becomes inoperative, place the IA key in the backup transceiver slot to start the vehicle. If the vehicle starts, that indicates the IA key is programmed, the backup transceiver, its circuitry to the RFA module, the RFA module, the start/stop switch and its circuitry to the RFA module, the PCM and all of the driveability components are OK. If the vehicle starts with the IA key in the backup slot, but cannot start with the IA key anywhere else in the vehicle interior, 1, 2 or all of the passive start antennas, the RFR module, the RFA module, the circuitry between the passive start antennas and the RFR module, or the circuitry between the RFR module, the RFA module may be at fault and the IA key battery may also be at fault. There may also be an RF interference issue in the area that is causing the problem. If the behavior is intermittent, it is likely an interference issue.
PATS uses a special ignition key, called an IA key that is larger than a conventional ignition key and looks more like a large Remote Keyless Entry (RKE) transmitter. It contains a permanently-installed electronic device called a transponder and has the RKE transmitter integrated into it. Each transponder contains a unique encrypted identification code which is one of a very large number of combinations. The IA key has a battery that should last the lifetime of the vehicle. Each IA key must be programmed into the RFA module before it can be used to start the vehicle. A maximum of 4 IA keys can be programmed to start the vehicle and operate the RKE functions. If more than 4 IA keys are attempted to be programmed, the message center in the IPC displays KEY PROGRAMMED, 4 KEYS TOTAL, then displays MAX # OF KEYS PROGRAMMED. There are special procedures described that must be carried out if a new IA key is necessary. Refer to Key Programming Using Two Programmed Keys - Intelligent Access (IA) With Intelligent Access (IA) or Key Programming Using Two Programmed Keys - Intelligent Access (IA) With Intelligent Access (IA).
Passive Start Antennas
There are 3 passive start antennas that are used solely for the purpose of starting the vehicle. They are located in the front of the floor console, in the rear of the floor console and on the floorpan, under the rear seat cushion. These 3 passive start antennas all receive a voltage (wake-up) signal from the RFA module when the start/stop button is pressed or when the brake pedal is pressed. Whenever a front door is opened and closed, this also causes a voltage signal to be sent to all of the passive start antennas. They send out a low frequency query in an effort to identify if any IA keys are within range of one of them. If an IA key is within range (approximately 1 m [3 ft]), the IA key sends a high frequency signal to the RFR module, which sends the key identification code to the RFA module over a hardwired circuit between the RFR module and the RFA module.
Backup Transceiver
The backup transceiver is located in the rear of the floor console and its associated backup transceiver slot is located in the floor console storage compartment. Make sure the transmitter buttons are facing forward and the key ring is up for the most efficient backup transceiver operation.
The backup transceiver can be used if the IA key battery fails or if the customer desires to keep the IA key out of sight. If the IA key battery fails, the passive start antennas cannot receive the IA key identification code and the vehicle experiences a PATS no-start. If the IA key is placed in the backup transceiver slot, the backup transceiver can read the key identification code and send it to the RFA module so the vehicle can be started. If the IA key is placed in the backup transceiver slot, the backup transceiver reads the IA key identification code and sends the data directly to the RFA module over hardwired circuits.
It is not recommended to leave the IA key in the backup transceiver slot as this decreases the security of the vehicle.
Whether the IA key identification code is read by the backup transceiver or by one of the passive start antennas, the RFA module validates the code, and if it is correct, sends a message to the PCM (OK-to-start) to ground the run/start relay solenoid coil and allow the fuel injectors to operate.
Passive Anti-Theft System (PATS) Operation
NOTE: The start/stop switch and the start/stop button verbiage may be used in place of each other to avoid confusion about the 2 separate functions each provide. Essentially, they are the same component and cannot be obtained separately.
The PATS function is controlled by the RFA module. With this type of PATS there are parameters that need to be reset if either the RFA module or the PCM (or both) are replaced. Refer to Passive Anti-Theft System (PATS) Parameter Reset - Intelligent Access (IA) With Intelligent Access (IA).
When the start/stop button and/or the brake pedal is pressed, the RFA module initiates the key interrogation sequence by sending a voltage (wake-up) signal to the 3 interior IA passive start antennas. The 3 passive start antennas send out a low frequency query to see if an IA key is within range (approximately a 1 m [3 ft] radius of each antenna). If an IA key is within range of 1 of the 3 passive start antennas, this process "reads" the PATS IA key identification code and sends the key identification code back to the RFA module, which interprets it and determines if it matches one of the stored keycodes.
If no IA key responds to the request from the 3 passive start antennas, the RFA module initiates communication with the backup transceiver. The transceiver then uses its antenna to bounce a signal off the transponder in the IA key (only if the IA key is in the backup slot). The backup transceiver also sends out a low frequency signal, but it only travels 77 mm (3.031 in).
If the IA key is in the backup slot, the key identification code is sent to the RFA module using the hardwired circuits between the backup transceiver and the RFA module. If the IA key is within range of 1 of the 3 passive start antennas, the antenna that is within range of the IA key sends a high frequency message to the RFR module. The RFR module sends the key identification code over a hardwired circuit to the RFA module. If it does match one of the stored keycodes, the RFA module turns on the run/start relay and sends a message to the PCM to ground the starter relay solenoid coil and allow the fuel injectors to operate. If it does not match one of the stored keycodes, or it is only a partial key read or no key read, the RFA module does not activate the run/start or run/accessory relays and the PCM never receives ignition run power.
All elements of PATS must be functional before the vehicle starts. If any of the components are not working correctly, the vehicle cannot start.
If the RFA module must be replaced for any reason (PATS issues or RFA module issues), the PATS IA keys must also be programmed into the new RFA module. Refer to Key Programming Using Two Programmed Keys - Intelligent Access (IA) With Intelligent Access (IA).
If the RFA module is replaced, the keyless entry keypad code in the SJB must be programmed into the new RFA module. Programmable Module Installation (PMI) does not resolve this. Refer to Keyless Entry Keypad Code Programming in Doors, Hood and Trunk &/or Locks. Testing and Inspection
A PATS no-start may involve a vehicle no-start due to either the fuel injectors not operating or the starter not operating (or both). A low battery voltage condition may cause the PATS to allow starter operation, but may keep the fuel injectors from operating.
PATS is not compatible with aftermarket remote start systems, which allow the vehicle to be started from the exterior of the vehicle. These systems can reduce the security of the vehicle, and can also cause no-start concerns. Remote start systems must be removed from the vehicle before any PATS-related no-start concerns are investigated.
Passive Anti-Theft System (PATS) PIDs
Monitoring the PATS PIDs can be very useful in determining which diagnostic steps to follow. Viewing the MASTERKEY PID (Master Key, verifies if the key is programmed) (with both keys) determines if the key is a programmed key and also proves-out the backup transceiver (if used), the passive start antenna that is being used (the one closest to the IA key), the RFR module, the circuitry and the RFA module. It is important to note that the MASTERKEY PID can only be read with the ignition in the ON mode. A master key is any key that is programmed into the RFA module. Viewing the MIN_KEYS PID (Minimum Keys, minimum number of keys necessary to start) (this PID does not change) indicates the minimum number of keys that must be programmed into the RFA module in order for the vehicle to start. There must be at least 2 keys programmed into the RFA module in this type of PATS before the vehicle starts. Viewing the N_KEYCODE PID (Number of Keys Programmed, number of keys that are programmed) determines if the minimum number of keys have been programmed into the RFA module. If the N_KEYCODE PID reads 0 or 1, additional key(s) need to be programmed into the RFA module in order to meet the minimum of 2 keys. If the N_KEYCODE PID reads 1, and the MASTERKEY PID reads Present (the ignition must be in the ON mode for this PID to read correctly), that particular key is already programmed into the RFA module.
When the parameters in the RFA module are reset, it clears (erases) the PCM ID (PCM_ID PID) from the RFA module. A PCM parameter reset causes the PCM to send a PCM ID to the RFA module that is necessary for the system to operate. Make sure to cycle the ignition at least once, then turn the ignition to ON, making an attempt to start the vehicle for 3-5 seconds before attempting more procedures. If only a PCM parameter reset occurs (or only an RFA module parameter reset occurs), the ID stored in the RFA module does not match the ID being sent by the PCM, and can cause a PATS-related no-start. Carry out the parameter reset, and do not cycle the key until after the parameter reset selection has been highlighted, and the IDS on-screen instructions have been followed. The IDS then resets the parameters in both the RFA module and the PCM at the same time. With Intelligent Access (IA)
If the PCM_VFY PID reads No, the PATSENABL PID reads Disabled, the N_KEYCODE PID reads 1 and the MASTERKEY PID reads Present (the ignition must be in the ON mode for this PID to read correctly), or if the N_KEYCODE PID reads 0 and the MASTERKEY PID reads Not Present (the ignition does not transition to ON with no keys programmed), a minimum of 2 keys need to be programmed into the RFA module. Refer to Key Programming Using Diagnostic Equipment - Intelligent Access (IA) With Intelligent Access (IA).
If the PCM_ID PID (PCM ID is stored) reads Stored, the RFA module has a PCM ID stored. If it reads Not Stored, a parameter reset of the PCM may resolve this concern. If the PCM_VFY PID (PCM Verify) reads No, the PATSENABL PID (PATS enable status) reads Disabled, the N_KEYCODE PID reads 2 or more and the MASTERKEY PID reads Present (the ignition must be in the ON mode for this PID to read correctly), the RFA module, and the PCM need to have their parameters reset. Refer to Passive Anti-Theft System (PATS) Parameter Reset - Intelligent Access (IA) With Intelligent Access (IA).
Cranking Factor PIDs
The Crk_Fact_B1 PID (Cranking Factor B1, Start/Stop button circuit 1) and the Crk_Fact_B2 PID (Cranking Factor B2, Start/Stop button circuit 2) must read YES, but it is only necessary for one of them to read YES as they are redundant circuits. If one of the start/stop button circuits fail, DTC B108A:15 (Start Button: Circuit Short To Battery Or Open) can set and if cleared, may not reappear. The start/stop button still operates using the backup circuit, but if the second circuit should also fail, the start/stop button cannot operate.
The Crk_Fact_Neu PID (Cranking Factor Neutral, vehicle is in neutral) or the Crk_Fact_Pk PID (Cranking Factor Park, vehicle is in park) must read YES in order to start the vehicle. Both of them cannot read YES, only one of them reading YES is necessary for the vehicle to start.
Spare Key Status PID
The SPAREKEY PID (Spare Key Status, spare key programming status) is defaulted to ENABLE. With the SPAREKEY PID displaying ENABLE, the RFA module accepts more than 2 keys (up to a maximum of 4) being programmed into the RFA module using the Key Programming Using Two Programmed Keys - Intelligent Access (IA) With Intelligent Access (IA) procedure. The SPAREKEY PID can be toggled to DISABLE if the customer wants to disable the customer spare key programming function. To enable or disable the spare key feature, refer to Key Programming Switch State Control - Intelligent Access (IA) With Intelligent Access (IA). This switch state control does not affect the Key Programming Using Diagnostic Equipment - With Intelligent Access (IA) procedure.
NOTE: The MASTERKEY PID cannot read accurately until the ignition is on. With the ignition in the off state, it always reads Not Present.
NOTE: The Crk_Fact_Neu and the Crk_Fact_Pk PIDs cannot both read YES. It is only necessary for one of them to read YES for the vehicle to start.
In summary, for the PATS PIDs and their correct state in order for the vehicle to start:
- Crk_Fact_B1 or Crk_Fact_B2 must read YES (preferably both should read YES, but vehicle starts with only one reading YES) (only reads YES with the Start/Stop button pressed). If the values do not match, and if the circuitry is OK, the start/stop switch should be replaced
- Crk_Fact_Brk must read YES (only reads YES with the brake pedal pressed)
- Crk_Fact_Neu must read YES (only reads YES if the vehicle transmission is in NEUTRAL (N) and Crk_Fact_Pk is NO)
- Crk_Fact_Pk must read YES (only reads YES if the vehicle transmission is in PARK (P) and Crk_Fact_Neu is NO)
- PCM_ID must read Stored
- N_KEYCODE must read a minimum of 2 (can read 3 or 4)
- MASTERKEY reads Not Present with the ignition OFF and Present with the ignition ON
- PCM_VFY must read Yes
- PATSENABL must read Enabled
Preliminary Checklist For A Passive Anti-Theft System (PATS) No-Start Vehicle
NOTE: If the IA key(s) can be read by the RFA module, the ignition mode changes to ON. In this case, there can be a parameter reset concern or the HS-CAN circuitry can be down. If the IA keys cannot be read by the RFA module, the ignition does not turn on. In this case, there can be an unprogrammed, or damaged IA key, a damaged passive start antenna, a damaged RFR module, a damaged RFA module or damaged circuitry.
Preliminary Checklist
Message Center Diagnostic Information
