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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: 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 anti-theft 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, the anti-theft 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 the anti-theft indicator.

A PATS (Passive Anti-Theft System) no-start may involve a vehicle no-start due to either the fuel injectors not operating or the starter not operating (or both). If the PATS (Passive Anti-Theft System) anti-theft indicator does not prove out and one (or both) of the previous conditions are present, it may be due to a PATS (Passive Anti-Theft System) concern. If the anti-theft indicator proves out, and the vehicle does not start, it is probably not a PATS (Passive Anti-Theft System) concern. Refer to the Computers and Control Systems Information. If the anti-theft indicator does not illuminate at all, it may be an IC (Instrument Cluster) concern.

Encoded Passive Anti-Theft System (PATS) Keys

NOTE: A maximum of 8 PATS (Passive Anti-Theft System) keys can be programmed into the IC (Instrument Cluster).

NOTE: A minimum of 2 keys must be programmed into the IC (Instrument Cluster) before the vehicle starts.

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 memory full DTC B1138. DTC B1138 is 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 IKT (Integrated Keyhead Transmitter) keys) start the vehicle, but cannot operate the RKE (Remote Keyless Entry) system. If additional PATS (Passive Anti-Theft System) keys are desired (more than 4, up to 8 total, IKT (Integrated Keyhead Transmitter) and PATS (Passive Anti-Theft System)), a standard PATS (Passive Anti-Theft System) key (a non-IKT (Integrated Keyhead Transmitter) key) can be used. There are special 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 .

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 also 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). With this type of PATS (Passive Anti-Theft System), there are parameters that need to be reset if either the IC (Instrument Cluster) or the PCM (or both) are replaced. Refer to Passive Anti-Theft System (PATS) Parameter Reset .

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 also 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 cannot start.

If the IC (Instrument Cluster) must be replaced for any reason (PATS (Passive Anti-Theft System) 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) will not disable a running vehicle.

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 can also prove 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) indicates the minimum number of keys that must be programmed into the IC (Instrument Cluster) in order for the vehicle to start. 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 has been programmed into the IC (Instrument Cluster). If the N_KEYCODE PID reads 0 or 1, additional key(s) needs 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). The SPAREKEY (spare key) PID is defaulted to ENABLE.

When the parameters in the IC (Instrument Cluster) are reset, it clears (erases) the PCM ID from the IC (Instrument Cluster). A PCM parameter reset causes the PCM to send a PCM ID to the IC (Instrument Cluster) that is necessary for the system to operate. Make sure to cycle the key at least once, then turn the key ON and make an attempt to start the vehicle for 3-5 seconds before attempting more procedures. If only a PCM parameter reset occurs, the ID stored in the IC (Instrument Cluster) will not match the ID being sent by the PCM, and can cause a PATS (Passive Anti-Theft System) -related no-start. Carry out the parameter reset, and do not cycle the key until after the parameter reset selection has been highlighted, and all of the following IDS (Integrated Diagnostic System) screens have been completed. The IDS (Integrated Diagnostic System) then resets the parameters in both the IC (Instrument Cluster) and the PCM at the same time.

If the PCM_ID reads Stored, the IC (Instrument Cluster) has a PCM ID stored. If it reads Not Stored, a parameter reset should resolve this concern. If the PCM_VFY PID (PCM verify) reads No, the N_KEYCODE PID reads 2 or more and the MASTERKEY PID reads Present, the IC (Instrument Cluster), and the PCM needs to have their parameters reset. Refer to 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 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 (Instrument Cluster). Refer to Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipment .

The SPAREKEY 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) using the 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 procedure. This switch state control does not affect the Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipment procedure.

In summary, for the PATS (Passive Anti-Theft System) 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

- PCM_VFY must read Yes

Unlimited Key Mode

This system contains a feature named unlimited key mode that has a PID of UNL_KEY_MODE (unlimited 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 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 electronically programmed to the vehicle is acceptable. Refer to Spare Key Programming - Unlimited Key Mode .
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