Passive Anti-Theft System (PATS) - Principles of Operation

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PASSIVE ANTI-THEFT SYSTEM (PATS) - HYBRID

See the Tribute Wiring Diagram for schematic information.

Principles of Operation

Anti-Theft Indicator

NOTE:Replacement of the passive anti-theft system (PATS) transceiver does not require the PATS keys to be programmed into the instrument cluster (IC) again.
NOTE:Make sure any aftermarket remote start systems have been removed from the vehicle before any PATS-related no-start concerns are investigated.
NOTE:A minimum of 2 PATS keys must be programmed into the IC before the vehicle will start.
NOTE:The smart junction box (SJB) is also known as the generic electronic module (GEM).
The PATS on the hybrid uses a visual anti-theft indicator located in the IC. The indicator proves out for 3 seconds when the ignition key is in the ON or START position under normal operation. If there is a PATS concern, this indicator either flashes rapidly or glows steadily when the ignition key is turned to the ON or START position. PATS also flashes the anti-theft indicator every 2 seconds when the ignition key is in the OFF position to act as a visual theft deterrent. Retrieve DTCs from the IC and the transmission control module (TCM) to determine if there are any PATS related DTCs that can indicate the cause of the no-start. See -- Symptom Troubleshooting Chart - Passive Anti-Theft System (PATS).
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 will not disable a running vehicle.
A PATS no-start may involve a vehicle no-start due to either the fuel injectors not operating or the Electronically Controlled Continuously Variable Transmission (eCVT) not cranking the engine (or both). If the PATS theft indicator does not prove out and one (or both) of the previous conditions are present, it can be due to a PATS concern. If the theft indicator proves out, and the vehicle does not start, it is probably not a PATS concern. See Quick Test. If the anti-theft indicator does not illuminate at all, it can be an IC concern. A low battery voltage can cause the PATS to allow the eCVT to crank the engine, but may keep the fuel injectors from operating.

Encoded PATS Keys

PATS uses a special ignition key, called an integrated keyhead transmitter (IKT) key that is larger than a conventional ignition key. It contains a permanently installed electronic device called a transponder and also has the remote keyless entry (RKE) transmitter integrated into the keyhead. Each transponder contains a unique encrypted identification code which is one of a very large number of combinations. The addition of this transponder to the key makes it an "encoded" key. The PATS key does not require batteries and should last the lifetime of the vehicle. The transmitter portion of the IKT key has a battery, which should last the lifetime of the vehicle. Each PATS key must be programmed into the IC before it can be used to start the vehicle. A maximum of 4 IKT keys can be programmed to start the vehicle and also operate the RKE functions. If more than 4 IKT keys are programmed, the RKE portion of the additional IKT key does not operate and the SJB (and the IC) sets a memory full DTC (B1138 - Memory Full). These additional keys start the vehicle, but do not operate the RKE system. If additional PATS keys are desired, a standard PATS key (a non-IKT key) can be used. There are special diagnostic procedures that must be carried out if a new PATS key is necessary. See Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipmentor Key Programming Using Two Programmed Keys.

PATS Transceiver

The PATS transceiver is located under the steering column shroud and communicates with the encoded ignition key. During each vehicle start sequence, the PATS transceiver reads the encoded ignition key identification code and sends data to the IC. The IC validates the code, and if it is the correct code, will send a message to the TCM to allow the eCVT to start the engine and sends a message to the PCM to allow the fuel injectors to operate.

PATS Operation

The PATS function is controlled by the IC. With this type of PATS, there are parameters that need to be reset if either the IC or the TCM (or both) are replaced. See Passive Anti-Theft System (PATS) Parameter Reset.
When the PATS key is turned to the ON or START position, the IC initiates the key interrogation sequence by sending a voltage signal to the PATS transceiver. The transceiver then uses its antenna to bounce a signal off the transponder in the PATS key. This process "reads" the PATS key identification code and sends the key identification code back to the IC, which interprets it and determines if it matches one of the stored key codes. If it does match one of the stored key codes, the IC will sends messages to the TCM to allow the eCVT to crank the engine and to the PCM to allow fuel injector operation. If it does not match one of the stored key codes, or it is only a partial key read or no key read, the IC will not allow the eCVT to start the engine and will not allow fuel injector operation. The anti-theft indicator in the IC will flash (or may glow steadily) and the IC will store one or more DTCs.
All elements of PATS must be functional before the vehicle will start. If any of the components are not working correctly, the vehicle does not start.
If the IC must be replaced for any reason (PATS concerns or IC concerns), the PATS keys must also be programmed into the new IC. See Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipment.
PATS disables the vehicle from starting if there is:

- a damaged PATS key.
- a non-programmed PATS key.
- a non-PATS key (key has no electronics).
- damaged wiring.
- a damaged transceiver.
- a damaged IC.
- a damaged TCM.

PATS PIDs

Monitoring the PATS PIDs can be very useful in determining which diagnostic steps to follow. Viewing the MASTERKEY (verifies if the key is programmed) PID with both keys determines if the key is a programmed key and may also be used to prove out the transceiver, circuitry and the IC. A master key is any key that is programmed into the IC. Viewing the MIN_KEY (minimum number of keys) PID (this PID does not change) determines the minimum number of keys that must be programmed into the IC. There must be at least 2 keys programmed into the IC in this type of PATS before the vehicle will start. Viewing the N_KEYCODE (number of keys programmed) PID will determine if the minimum number of keys have been programmed into the IC. If the N_KEYCODE PID reads 0 or 1, additional key(s) will need to be programmed into the IC in order to meet the minimum of 2 keys. If the N_KEYCODE PID reads 0 or 1, and the MASTERKEY PID reads NOTPREST, that particular key must be programmed into the IC. If the N_KEYCODE PID reads 1, and the MASTERKEY PID reads PRESNT, that particular key is already programmed into the IC. If the IC was replaced, the parameters in the IC, and the parameters in the TCM need to be reset.
When the parameters are reset, it clears (erases) the TCM ID from the IC and the IC ID from the TCM. Make sure to cycle the key at least once, then turn the key to the ON position and make an attempt to start the vehicle for 3-5 seconds before attempting more procedures. If only a TCM parameter reset occurs (if a TCM is replaced), the ID stored in the IC does not match the ID being sent by the TCM, and can cause a PATS-related no-start. Carry out the parameter reset in order to resolve these concerns.
If the TCM ID PID reads STORED, the IC has a TCM ID stored. If it reads NOTSTRD, a parameter reset of the TCM can resolve this concern. If the PCM_VFY PID reads NO, the N_KEYCODE PID reads 2 or more and the MASTERKEY PID reads PRESNT, the IC, and the TCM need to have their parameters reset. See Passive Anti-Theft System (PATS) Parameter Reset.
If the PCM_VFY PID reads NO, the N_KEYCODE PID reads 1 and the MASTERKEY PID reads PRESNT, or if the N_KEYCODE PID reads 0 and the MASTERKEY PID reads NOTPRESNT, a minimum of 2 keys will need to be programmed into the IC. See Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipment.
If the MASTERKEY PID continues to read NOTPRESNT after programming, this can indicate a defective key. The SPAREKEY PID is defaulted to ENABLE. With the SPAREKEY PID displaying ENABLE, the IC accepts more than 2 keys (up to a maximum of 8) being programmed into the IC. See Key Programming Using Two Programmed Keys. It can be toggled to DISABL if the customer wants to disable the customer spare key programming function. See Key Programming Switch State Control. This switch state control does not affect the Key Programming Using Diagnostic Equipment procedure.
In summary, for the vehicle to start, the PATS PIDs and their correct state are:

- N_KEYCODE must read 2 or more
- MASTERKEY must read PRESNT
- TCM ID must read STORED
- PCM_VFY must read YES

Unlimited Key Mode

This system contains a feature called unlimited key mode (PID UNL_KEY_ID). This feature allows a customer to program more than 8 keys to their vehicle if they request it. Each vehicle in unlimited key mode is set up with a special unlimited transponder security key code. This allows all the customer vehicles to share the same mechanically cut keys, but no other keys from outside can be used to operate the vehicles. For an individual customer, any randomly selected security key that has been previously mechanically cut and is electronically programmed to the vehicle is acceptable. See - Spare Key Programming - Unlimited Key Mode.