Principles Of Operation

Anti-Theft

Principles of Operation

NOTE: A minimum of 2 IA keys must be programmed into the RFA module before the vehicle can start.

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 Instrumentation, Message Center, and Warning Chimes Description and Operation 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 does not 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: The IA key must be outside the vehicle for entry purposes, and inside the vehicle for starting purposes. The IA key cannot operate the system if used in the opposite manner. In other words, the IA key cannot be used for entry if it is inside of the vehicle and it cannot be used for starting if it is outside of the vehicle. This is done for security purposes. If an IA key is inside the vehicle, and the operator is carrying another programmed IA key, IA entry is still allowed.

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 and 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 Key Programming Using Two Programmed Keys or Key Programming Using Diagnostic Equipment Key Programming Using Diagnostic Equipment.

Passive Start Antennas

There are 3 IA passive start antennas that are used solely for the purpose of starting the vehicle. They are located in the front of the center floor console, in the rear of the center 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 switch is pressed, when the brake pedal is pressed or when a front door is opened. 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 and its associated backup transceiver slot are located in the glove compartment. This slot allows the IA key to be placed in close proximity to the backup transceiver for starting purposes. If the vehicle does not start, place the IA key in the backup transceiver slot and attempt to start the vehicle. Make sure the transmitter buttons are facing rearward and that the key ring is in the up position.

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. During each vehicle start sequence, the 3 passive start antennas all send a low frequency query to determine if there are any IA keys within their range. If no IA key is found within range, the RFA module activates the backup transceiver. Each passive start antenna range is approximately 1 m (3 ft) and the backup transceiver range is approximately 77 mm (3.031 in). 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

The Passive Anti-Theft System (PATS) function is controlled by the RFA module and PCM.

When the start/stop button and/or the brake pedal is pressed, the RFA module initiates the key interrogation sequence by activating the 3 interior IA passive start antennas. Each passive start antenna sends out a low frequency signal approximately 1 m (3 ft) radius of each antenna. If an IA key is within range of 1 of the 3 interior passive start antennas, the IA key is activated. Once the IA key is activated, it sends the PATS identification code to the RFR module via a high frequency signal. The RFR module interprets the high frequency signal from the IA key and sends the information to the RFA module over a dedicated network. If the RFA module determines that a programmed IA key is inside the vehicle, it allows the ignition to be transitioned out of the OFF mode. If the operator requests the engine to start, a signal is sent to the PCM over the High Speed Controller Area Network (HS-CAN) to allow the fuel injectors and starter to operate.

If the vehicle has a failure of any passive start antenna, the battery in the IA key, or the RFR module, the vehicle can experience a PATS no-start. However, in the event of one of these failures, the IA key can be placed in the backup slot (located in the center console) to allow the vehicle to start. The backup transceiver is located next to the backup slot and activates an IA key if it is placed in the slot. The backup transceiver is hardwired to the RFA module and when it is activated, sends out a low frequency signal that only travels 77 mm (3.031 in). If a programmed IA key is in the backup slot when the backup transceiver is activated, it activates the IA key and the identification code is sent back to the RFA module through the backup transceiver.

The RFA module activates all passive start antennas to search the inside of the vehicle for an IA key anytime a door or liftgate is opened or closed. This strategy is used to prevent the IA key from being separated from an already running vehicle.

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.

PATS and the RKE system share the operation of several components including the IA key and the RFR module. If there is a concern with either of these components, both PATS and the RKE system are affected. Refer to Handles, Locks, Latches and Entry Systems Description and Operation for information on the RKE and IA features.

The RFA module also controls the ignition modes and in conjunction with the PCM controls One-Touch Integrated Start (OTIS). If there is a concern with OTIS or the ignition modes, and PATS has been eliminated as the cause, refer to Starting System Testing and Inspection for OTIS or Steering Column Switches Testing and Inspection for the ignition modes.

PATS disables the vehicle from starting if there is:

- a damaged PATS IA key.
- a non-programmed PATS IA key.
- a non- PATS IA key (key has no electronics).
- damaged wiring.
- a damaged backup transceiver (only if the IA key is in the backup slot).
- a damaged passive start antenna.
- a damaged Remote Functions Receiver (RFR) module.
- a damaged RFA module.
- a damaged PCM.

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 (PATs MasterKey Present, 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 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 Passive Anti-Theft System (PATS) Parameter Reset, and do not cycle the key until after the parameter reset selection has been highlighted, and the on-screen instructions have been followed. The IDS then resets the parameters in both the RFA module and the PCM at the same time.

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 (PATS ok to start) reads Yes, the PATSENABL PID (PATS status) reads Disabled, the N_KEYCODE PID reads 2 or more and the MASTERKEY PID reads YES (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 Programming and Relearning.

Cranking Factor PIDs

The Crk_Fact_B1 PID (Cranking Factor B1, start/stop switch circuit 1) and the Crk_Fact_B2 PID (Cranking Factor B2, start/stop switch 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 switch circuits fail, DTC B108A:15 (Start Button: Circuit Short To Battery Or Open) can set and if cleared, may not reappear. The start/stop switch still operates using the backup circuit, but if the second circuit should also fail, the start/stop switch 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.

If the PCM_VFY PID reads Yes, 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 NO (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 Key Programming Using Diagnostic Equipment.

Spare Key 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 Key Programming Using Two Programmed Keys 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 the Key Programming Switch State Control Key Programming Switch State Control procedure. This switch state control does not affect the Key Programming Using Diagnostic Equipment procedure.

NOTE: The MASTERKEY PID cannot read accurately until the ignition is on. With the ignition in the off state, it always reads NO.

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 switch 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 and Crk_Fact_Pk is NO)
- Crk_Fact_Pk must read YES (only reads YES if the vehicle transmission is in park 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 antenna, a damaged RFR module, a damaged RFA module or damaged circuitry.

Preliminary Vehicle Checklist





Diagnostic Information from Message Center





Field-Effect Transistor (FET) Protection

Field-Effect Transistor (FET) is a type of transistor that when used with module software can be used to monitor and control current flow on module outputs. The FET protection strategy is used to prevent module damage in the event of excessive current flow.

The RFA module utilizes a FET protective circuit strategy for many of its outputs (for example, a headlamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the voltage or ground provided by the module) when a fault event is detected. A continuous DTC is stored at the fault event and a cumulative counter is started.

When the demand for the output is no longer present, the module resets the FET circuit protection to allow the circuit to function. The next time the driver requests a circuit to activate that has been shut down by a previous short (FET protection) and the circuit remains shorted, the FET protection shuts off the circuit again and the cumulative counter advances.

When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. Each FET protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the FET and the ability of the FET to withstand it. A module lifetime level of fault events is established based upon the durability of the FET. If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.

When each tolerance level is reached, the continuous DTC that was stored on the first failure cannot be cleared by a command to clear the continuous DTCs. The module does not allow this code to be cleared or the circuit restored to normal operation until a successful self-test proves that the fault has been repaired. After the self-test has successfully completed (no on-demand DTCs present), DTC U1000:00 and the associated continuous DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When the first or second level is reached, the continuous DTC (associated with the short circuit) sets along with DTC U1000:00. These DTCs can be cleared using the module on-demand self-test, then the Clear DTC operation on the scan tool (if the on-demand test shows the fault corrected). The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach the third level, then DTC U3000:49 sets along with the associated continuous DTC. This DTC cannot be cleared and the module must be replaced.

The only RFA module FET protected output circuit for PATS are the backup transceiver voltage circuit and the start/stop switch run LED voltage circuit.