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Principles of Operation




Anti-Theft

Principles of Operation

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

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: A minimum of 2 PATS keys must be programmed into the IC before the vehicle starts.

NOTE: Make sure any aftermarket remote start systems have been removed from the vehicle before any PATS-related no-start concerns are investigated.

PATS 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.

Encoded Passive Anti-Theft System (PATS) Keys

PATS uses a special ignition key that is larger than a conventional ignition key because it contains a permanently installed electronic device called a transponder. 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. Each PATS key must be programmed into the IC before it can be used to start the vehicle. There are special general procedures described that must be carried out if a new PATS key is necessary. Refer to Key Programming Using Diagnostic Equipment Using Diagnostic Equipment or Key Programming Using Two Programmed Keys Using Two Programmed Keys.

MyKey(TM) Feature

The MyKey(TM) feature allows the customer to program a restricted driving mode on one (or more) key(s) supplied with the vehicle or any programmed spare key(s) to promote good driving habits. The MyKey(TM) is a restricted key for all consecutive key cycles until the MyKey(TM) restricted key is disabled. The remaining key is referred to as an "administrator key" or admin key. There must always be at least one admin key. Both the admin key and the MyKey(TM) key can be used to see how many MyKey(TM) and admin keys are programmed to the vehicle, and how many total miles have been driven with the MyKey(TM) restricted key active.

Refer to Information and Message Center in the Description and Operation portion of Instrument Panel, Gauges and Warning Indicators for MyKey(TM) system checks and system warning displays.

Refer to MyKey(TM) Programming for programming information.

Passive Anti-Theft System (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, sends a message over the High Speed Controller Area Network (HS-CAN) to the PCM to ground the starter relay solenoid coil and allow the fuel injectors to operate.

Passive Anti-Theft System (PATS) Operation

The PATS function is controlled by the IC. When the ignition switch 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 communicate with 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 PCM grounds the starter relay solenoid coil and allows 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 sends a message over the HS-CAN to the PCM to not ground the starter relay solenoid coil and not allow fuel injector operation. The anti-theft indicator in the IC flashes (or may glow steadily) and the IC stores one or more DTCs. All elements of PATS must be functional before the vehicle can start. If any of the components are not working correctly, the vehicle cannot start. If the IC must be replaced for any reason (PATS concerns or IC concerns), the PATS keys must be programmed into the new IC. Refer to Key Programming Using Diagnostic Equipment Using Diagnostic Equipment.

PATS is not compatible with aftermarket remote start systems, which allow the vehicle to be started from the exterior of the vehicle. These systems may reduce the security of the vehicle and also may be the cause of 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 in the IC 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 also proves out the transceiver, circuitry and the IC. A master key is any key that is programmed into the IC (the MASTERKEY PID must display Present). If the MASTERKEY PID reads Not Present, it may mean the key in the ignition lock cylinder is not programmed, is not a PATS key, is inoperative, or the transceiver, circuitry or IC may be at fault.

Viewing the MIN_KEYS (minimum number of keys) PID (this PID does not change) indicates 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 starts.

Viewing the N_KEYCODE (number of keys programmed) PID determines if the minimum number of keys have been programmed into the IC. If the N_KEYCODE PID reads 0 or 1, additional key(s) 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 Not Present, that particular key must be programmed into the IC. If the N_KEYCODE PID reads 1, and the MASTERKEY PID reads Present, that particular key is already programmed into the IC.

If the IC was replaced, the parameters in the IC, then the parameters in the PCM need to be reset. When the parameters in the IC are reset, it clears (erases) the PCM ID from the IC. A parameter reset of the PCM sends a PCM ID to the IC that is necessary for the system to operate. Make sure to make 3-5 attempts to start the vehicle for 3-5 seconds each before attempting more procedures. The extra key cycles are necessary for the PCM ID to be sent (by the PCM) and then stored by the IC. If only a PCM parameter reset occurs, the IC may encounter 2 PCM IDs (the original one and the new one) and may cause a PATS-related no-start. If the PCM_ID PID reads Stored, the IC has a PCM ID stored. If it reads Not Stored, a parameter reset of the PCM may resolve this issue. If the PCM_ID PID reads Stored, the PCM_VFY (the PCM ID has been verified) PID reads Yes.

If the PATSENABL PID reads Disabled, and the N_KEYCODE PID reads 2 or more and the MASTERKEY PID reads Present, the IC and the PCM need to have their parameters reset.

If the PATSENABL PID reads Disabled, and the N_KEYCODE PID reads 1 and the MASTERKEY PID reads Present, or if the N_KEYCODE PID reads 0 and the MASTERKEY PID reads Not Present, a minimum of 2 keys need to be programmed into the IC. Refer to Key Programming Using Diagnostic Equipment Using Diagnostic Equipment.

If the MASTERKEY continues to read Not Present after programming, this may indicate a defective key. The SPAREKEY (spare key) 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. Refer to Key Programming Using Two Programmed Keys Using Two Programmed Keys. It can be toggled to DISABLE if the customer does not want any more than 2 keys programmed into the IC. Refer to Key Programming Switch State Control Switch State Control. This switch state control does not affect the Key Programming Using Diagnostic Equipment procedure.

In summary for the IC PATS PIDs and their correct state in order for the vehicle to start:

- N_KEYCODE must read 2 or more
- MASTERKEY must read Present
- PCM_ID must read Stored
- PATSENABL must read Enabled
- PCM_VFY must read Yes

Unlimited Key Mode

PATS contains a feature named unlimited key mode (PID of UNL_KEY_MODE). 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's vehicles to share the same mechanically cut keys, but no other keys from outside can be used to operate the vehicle(s). Any randomly selected security key that has been previously mechanically cut and electronically programmed to the vehicle is acceptable. Refer to Spare Key Programming - Unlimited Key Mode Unlimited Key Mode.
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