Antitheft and Alarm Systems: Description and Operation

Anti-Theft

The Passive Anti-Theft System (PATS) consists of the following components:

- Anti-theft indicator (located in the Instrument Cluster (IC))
- Encoded (the key contains a transponder) ignition key
- PATS transceiver (located around the ignition lock cylinder under the steering column shroud)
- IC

PATS uses radio frequency identification technology to deter a drive-away theft. Passive means that it does not require any activity by the user.

The vehicle is equipped with 2 PATS keys. A maximum of 8 PATS keys can be programmed to start the vehicle. If additional PATS keys are desired, refer to Spare Key Programming - Unlimited Key Mode Unlimited Key Mode.

Passive Anti-Theft System (PATS) Function

The PATS function is controlled by the IC. PATS uses the IC to carry out all of the PATS functions such as receiving the identification code from the PATS key, controlling the starter and fuel injectors enable, and initiates the key interrogation sequence when the ignition key is turned to the ON or START position. All elements of PATS must be functional before the vehicle starts. If any of the components are not working correctly, the vehicle will not 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 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.

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.

A PATS no-start may involve a vehicle no-start due to either the fuel injectors not operating or the starter not operating (starter relay does not close) or both.

PATS disables the vehicle from starting if there is:

- a damaged PATS key.
- an unprogrammed PATS key.
- a non-PATS key (a conventional key or one that does not have any electronics).
- damaged wiring, terminals or connectors.
- a damaged transceiver.
- a damaged IC.

Unlimited Key Mode

PATS contains a feature called unlimited key mode. This feature allows a customer to program more than 8 vehicle keys, if requested. Each vehicle in unlimited key mode is set up with a special, unlimited transponder security key code. This allows all the customer vehicles (or, one vehicle) to share the same mechanically cut keys (more than 8 keys). 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 Unlimited Key Mode.