Antitheft and Alarm Systems: Description and Operation
ANTI-THEFTThe passive anti-theft system (PATS) consists of the following components:
- Anti-theft indicator (located in the instrument cluster)
- Encoded ignition integrated keyhead transmitter (IKT) PATS key(s) (the key contains a transponder and a remote keyless entry [RKE] transmitter)
- Encoded (the key contains a transponder) ignition PATS keys (not factory equipped, but may be used in place of IKT keys)
- PATS transceiver
- Instrument cluster
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 IKT PATS keys. The IKTs operate as a standard PATS key with an RKE transmitter incorporated into the keyhead. The IKTs require batteries for the RKE transmitter to operate. A maximum of 4 IKT keys can be programmed to operate the vehicle. If more than 4 IKT keys are programmed, the RKE portion of the additional keys do not operate and the smart junction box (SJB) and the instrument cluster set a memory full diagnostic trouble code (DTC) (B1138 - Memory Full). These additional keys will start the vehicle, but will not operate the RKE system. If additional PATS keys are desired, a standard PATS key (a non-IKT key) can be used. For the purposes, the PATS portion of the IKT key is referred to as a PATS key.
PATS Function
NOTE: If the instrument cluster or the PCM (or both) is replaced, the parameters must be re-set in both modules or the vehicle will experience a PATS no-start. For additional information, refer to Passive Anti-Theft System (PATS) Parameter Reset. Passive Anti-Theft System (PATS) Parameter Reset
The PATS function is controlled by the instrument cluster. The PATS uses the instrument cluster to carry out all of the PATS functions such as receiving the identification code from the PATS key, issuing a signal to the PCM to control the starter and fuel injectors enable, and initiating the key interrogation sequence when the ignition key is turned to the ON or START position. Because of the interaction between the instrument cluster and the PCM, there are parameters that must be set if the instrument cluster or the PCM (or both) are replaced. For additional information, refer to Passive Anti-Theft System (PATS) Parameter Reset. If the instrument cluster must be replaced for any reason (PATS concerns or an instrument cluster concern), the PATS keys also must be programmed into the new instrument cluster. For additional information, refer to Integrated Keyhead Transmitter (IKT) Key Programming Using Diagnostic Equipment. All elements of PATS must be functional before the vehicle will start. If any of the components are not working correctly, the vehicle will not start. Passive Anti-Theft System (PATS) Parameter Reset 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 may cause a vehicle no start due to either the fuel injectors or the starter not operating (starter relay does not close) or both. Always check for PATS DTCs from the instrument cluster and DTCs from the PCM when a no-crank or no-start condition exists. A low state of charge (SOC) in the vehicle battery may cause the PATS to allow starter operation, but prevent the fuel injectors from operating.
If the theft light 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 issue. If the theft light proves out, it may not be a PATS issue. If the theft light does not illuminate at all, it may be an instrument cluster issue. For additional information, refer to Anti-Theft, Symptom Chart in the Diagnosis and Testing portion. Symptom Related Diagnostic Procedures
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.
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 to share the same mechanically cut keys. For an individual customer, any randomly selected security key is acceptable.
If unlimited key mode is enabled, a maximum of 4 IKT keys can be programmed to the vehicle for RKE functionality. If more keys are required, they should be standard PATS keys. If more than 4 IKT keys are programmed to the vehicle, the smart junction box (SJB) and the instrument cluster will set DTC B1138 (memory full) and only 4 IKT keys will have RKE functionality, however, all of them will start the vehicle, if programmed correctly. For additional information, refer to Spare Key Programming - Unlimited Key Mode. Unlimited Key Mode