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Principles Of Operation




Anti-Theft

Principles of Operation

NOTE: Replacement of the Passive Anti-Theft System (PATS) transceiver does not require the PATS (Passive Anti-Theft System) 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 (Passive Anti-Theft System) -related no-start concerns are investigated.

NOTE: A minimum of 2 PATS (Passive Anti-Theft System) keys must be programmed into the IC (Instrument Cluster) before the vehicle starts.

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

Anti-Theft Indicator

PATS (Passive Anti-Theft System) uses a visual anti-theft indicator located in the IC (Instrument Cluster). 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 (Passive Anti-Theft System) concern, this indicator either flashes rapidly or glows steadily when the ignition key is turned to the ON or START position. PATS (Passive Anti-Theft System) 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. for information on the anti-theft indicator.

Encoded Passive Anti-Theft System (PATS) Keys

PATS (Passive Anti-Theft System) 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 (Passive Anti-Theft System) key does not require batteries and should last the lifetime of the vehicle. The transmitter portion of the IKT (Integrated Keyhead Transmitter) key has a battery. Each PATS (Passive Anti-Theft System) key must be programmed into the IC (Instrument Cluster) before it can be used to start the vehicle. A maximum of 4 IKT (Integrated Keyhead Transmitter) keys can be programmed to start the vehicle and also operate the RKE (Remote Keyless Entry) functions. If more than 4 IKT (Integrated Keyhead Transmitter) keys are programmed, the RKE (Remote Keyless Entry) portion of the additional IKT (Integrated Keyhead Transmitter) keys does not operate and the SJB (Smart Junction Box) sets a memory full DTC (B1138 - Memory Full). The same DTC id also flagged in the IC (Instrument Cluster). The memory that is full is referring to the memory in the SJB (Smart Junction Box). These additional keys (more than 4 IKTs (Integrated Keyhead Transmitters)) starts the vehicle, but does not operate the RKE (Remote Keyless Entry) system. If additional PATS (Passive Anti-Theft System) keys are desired, a standard PATS (Passive Anti-Theft System) key (a non-IKT (Integrated Keyhead Transmitter) key) can be used. There are special diagnostic procedures described that must be carried out if a new PATS (Passive Anti-Theft System) key is necessary. Refer to Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipment or Key Programming Using Two Programmed Keys .

Factory Invoiced Accessory (FIA) Remote Starter

Vehicles may be equipped with a dealer-installed factory-invoiced remote start system that is a Factory Invoiced Accessory (FIA). The remote start fob for this system uses a small device that is about half the size of a conventional RKE (Remote Keyless Entry) fob, but only has one button on it. If the remote start system is installed on the vehicle and the unlimited mode is not enabled, the PATS (Passive Anti-Theft System) allows up to 7 PATS (Passive Anti-Theft System) keys to be programmed into the Instrument Cluster (IC). The remote start system uses up 1 of the 8 total PATS (Passive Anti-Theft System) keys that can be programmed into the IC (Instrument Cluster). The number of keys that are programmed into the PATS (Passive Anti-Theft System) can be determined by viewing the IC (Instrument Cluster) PID N_KEYCODE.

Passive Anti-Theft System (PATS) Transceiver

The PATS (Passive Anti-Theft System) transceiver is located under the steering column shroud and communicates with the encoded ignition key. During each vehicle start sequence, the PATS (Passive Anti-Theft System) transceiver reads the encoded ignition key identification code and sends data to the IC (Instrument Cluster). The IC (Instrument Cluster) validates the code, and if it is the correct code, sends a message 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 (Passive Anti-Theft System) function is controlled by the IC (Instrument Cluster). When the PATS (Passive Anti-Theft System) key is turned to the ON or START position, the IC (Instrument Cluster) initiates the key interrogation sequence by sending a voltage signal to the PATS (Passive Anti-Theft System) transceiver. The transceiver then uses its antenna to bounce a signal off the transponder in the PATS (Passive Anti-Theft System) key. This process "reads" the PATS (Passive Anti-Theft System) key identification code and sends the key identification code back to the IC (Instrument Cluster), 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 (Instrument Cluster) 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 key codes, or it is only a partial key read or no key read, the IC (Instrument Cluster) sends a message to the PCM to not ground the starter relay solenoid coil and not allow fuel injector operation. The anti-theft indicator in the IC (Instrument Cluster) flashes (or may glow steadily) and the IC (Instrument Cluster) stores one or more DTCs. All elements of PATS (Passive Anti-Theft System) must be functional before the vehicle starts. If any of the components are not working correctly, the vehicle does not start. If the IC (Instrument Cluster) must be replaced for any reason (PATS (Passive Anti-Theft System) concerns or IC (Instrument Cluster) concerns), the PATS (Passive Anti-Theft System) keys must also be programmed into the new IC (Instrument Cluster). Refer to Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipment .

PATS (Passive Anti-Theft System) is active only for a few seconds when the vehicle is starting. It is not a PATS (Passive Anti-Theft System) concern if the vehicle stalls after it has been running for a minimum of 3 seconds. PATS (Passive Anti-Theft System) does not disable a running vehicle.

The PATS (Passive Anti-Theft System) may cause a vehicle no start due to either the fuel injectors not operating or the starter not operating (starter relay does not close) or both. Always check for PATS (Passive Anti-Theft System) DTCs in the IC (Instrument Cluster) and the PCM when a no-crank or no-start condition exists. A low state of charge in the vehicle battery may cause the PATS (Passive Anti-Theft System) to allow starter operation, but prevent the fuel injectors from operating. If the anti-theft indicator does not prove out (it may be either flashing or glowing steadily) and one (or both) of the previous conditions (fuel injectors and/or starter inoperative) are present, it may be due to a PATS (Passive Anti-Theft System) concern. If the anti-theft indicator proves out, it may not be a PATS (Passive Anti-Theft System) concern. If the anti-theft indicator does not illuminate at all, it may be an IC (Instrument Cluster) concern. GO to Symptom Chart. Anti-Theft - Passive Anti-Theft System (PATS)

PATS (Passive Anti-Theft System) 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 may also be the cause of no-start concerns. Remote start systems must be removed from the vehicle before any PATS (Passive Anti-Theft System) -related no-start concerns are investigated. If the remote start system is a Power Code(R) system, make certain it is not the cause of the no-start. Removal of the system may be necessary.

PATS (Passive Anti-Theft System) disables the vehicle from starting if there is:

- a damaged PATS (Passive Anti-Theft System) key.

- a non-programmed PATS (Passive Anti-Theft System) key.

- a non-PATS (Passive Anti-Theft System) key (key has no electronics).

- damaged wiring.

- a damaged transceiver.

- a damaged IC (Instrument Cluster).

- a damaged PCM.

Passive Anti-Theft System (PATS) PIDs

Monitoring the PATS (Passive Anti-Theft System) 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 also proves out the transceiver, circuitry and the IC (Instrument Cluster). A master key is any key that is programmed into the IC (Instrument Cluster).

Viewing the MIN_KEYS (minimum number of keys) PID (this PID does not change) determines the minimum number of keys that must be programmed into the IC (Instrument Cluster). There must be at least 2 keys programmed into the IC (Instrument Cluster) in this type of PATS (Passive Anti-Theft System) 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 (Instrument Cluster). If the N_KEYCODE PID reads 0 or 1, additional key(s) need to be programmed into the IC (Instrument Cluster) 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 (Instrument Cluster). If the N_KEYCODE PID reads 1, and the MASTERKEY PID reads Present, that particular key is already programmed into the IC (Instrument Cluster).

If the IC (Instrument Cluster) was replaced, the parameters in the IC (Instrument Cluster), and the parameters in the PCM need to be reset. When the parameters in the IC (Instrument Cluster) are reset, that clears (erases) the PCM ID from the IC (Instrument Cluster). A parameter reset of the PCM sends a PCM ID to the IC (Instrument Cluster) that is necessary for the system to operate. After the parameter resets, make sure to make 3-5 attempts to start the vehicle for 3-5 seconds each time 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 (Instrument Cluster). If only a PCM parameter reset occurs, the IC (Instrument Cluster) may encounter 2 PCM IDs (the original one and the new one) and may cause a PATS (Passive Anti-Theft System) -related no-start. If a PCM parameter reset occurs first, then the IC (Instrument Cluster) parameter reset occurs, no PCM IDs store in the IC (Instrument Cluster), and a PATS (Passive Anti-Theft System) -related no-start may occur. Note that when using the Integrated Diagnostic System (IDS), both parameter resets occur at the same time. If the PCM_ID (PCM ID status) PID reads Stored, the IC (Instrument Cluster) has a PCM ID stored. If it reads Not Stored, a Keep Alive Memory (KAM) reset of the PCM may resolve this concern (or, use the IDS (Integrated Diagnostic System) to reset the parameters in both the PCM and the IC (Instrument Cluster) at the same time). If the PATSENABL (vehicle enable status) PID reads Enabled, and the N_KEYCODE reads 2 or more and the MASTERKEY reads Present, the IC (Instrument Cluster) and the PCM need to have their parameters reset.

If the PATSENABL reads Disabled, and the N_KEYCODE reads 1 and the MASTERKEY reads Present, or if the N_KEYCODE reads 0 and the MASTERKEY reads Not Present, a minimum of 2 keys need to be programmed into the IC (Instrument Cluster). Refer to Integrated Keyhead Transmitter (IKT) Key Programming 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 (Instrument Cluster) accepts more than 2 keys (up to a maximum of 8) being programmed into the IC (Instrument Cluster). Refer to Key Programming 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 (Instrument Cluster). Refer to Key Programming Switch State Control . This switch state control does not affect the Key Programming Using Diagnostic Equipment procedure.

In summary, the PATS (Passive Anti-Theft System) PIDs and their correct state in order for the vehicle to start are:

- N_KEYCODE must read 2 or more

- MASTERKEY must read Present

- PCM_ID must read Stored

- PCM_VFY must read Yes

- PATSENABL must read Enabled

Unlimited Key Mode

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