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Principles of Operation




Anti-Theft

Principles of Operation

Anti-Theft Indicator

NOTE: Make sure to determine if the vehicle is equipped with Passive Anti-Theft System (PATS) before following any PATS (Passive Anti-Theft System) -related diagnostics. PATS (Passive Anti-Theft System) is optional on this vehicle.

NOTE: Replacement of the PATS (Passive Anti-Theft System) 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: If the IC (Instrument Cluster) or the PCM is being replaced (or both), the parameters must be reset in both modules or the vehicle experiences a PATS (Passive Anti-Theft System) no-start. This occurs even if the vehicle is not equipped with PATS (Passive Anti-Theft System). Refer to Passive Anti-Theft System (PATS) Parameter Reset .

The PATS (Passive Anti-Theft System) 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. If the vehicle is not equipped with PATS (Passive Anti-Theft System), the anti-theft indicator does not flash with the key in the OFF position. Refer to Instrument Panel, Gauges and Warning Indicators for information on the anti-theft indicator.

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) can not disable a running vehicle.

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) issue. If the anti-theft indicator proves-out, and the vehicle does not start, it is probably not a PATS (Passive Anti-Theft System) issue. 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) issue. GO to Symptom Chart. Symptom Related Diagnostic Procedures A low battery voltage may cause the PATS (Passive Anti-Theft System) to allow starter operation, but may keep the fuel injectors from operating.

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 the data to the IC (Instrument Cluster). The IC (Instrument Cluster) validates the code, and if it is the correct code, the IC (Instrument Cluster) sends a message to the PCM to ground the starter relay solenoid coil and to also allow the fuel injectors to operate. Refer to Passive Anti-Theft System (PATS) Transceiver .

Passive Anti-Theft System (PATS) Operation

NOTE: If the IC (Instrument Cluster) or the PCM is being replaced (or both), the parameters must be reset in both modules or the vehicle experiences a PATS (Passive Anti-Theft System) no-start. This occurs even if the vehicle is not equipped with PATS (Passive Anti-Theft System). PATS (Passive Anti-Theft System) vehicles and non-PATS (Passive Anti-Theft System) vehicles have parameters in the IC (Instrument Cluster) and the PCM and they must be reset whenever either (or both) module(s) is (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 to 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.

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 parameter reset is necessary.

- 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 may also be used to 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) 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 PCM need to be reset.

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) does not match the ID being sent by the PCM, and may cause a PATS (Passive Anti-Theft System) -related no-start.

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 parameter reset may resolve this issue. If the PCM_VFY (PCM verify status) PID reads No, 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. Refer to Passive Anti-Theft System (PATS) Parameter Reset . In this particular scenario, the PATSENABL (vehicle enable status) PID reads Disabled.

If the PCM_VFY PID reads No, 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 (Instrument Cluster). Refer to Key Programming Using Diagnostic Equipment .

If the MASTERKEY PID continues to read Not Present after programming, this may indicate an inoperative 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) using Key Programming Using Two Programmed Keys . It can be toggled to DISABLE if the customer wants to disable the customer spare key programming function. Refer to Key Programming Switch State Control . This switch state control does not affect the Key Programming Using Diagnostic Equipment procedure.

Also, if the unlimited key mode has been enabled, the N_KEYCODE PID always reads 2 after the first 2 keys have been programmed into the IC (Instrument Cluster). If more than 2 keys are programmed, the N_KEYCODE PID always reads 2.

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

- PATSENABL must read Enabled
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