Module, Intrusion Transceiver (ITM): Operation

WARNING: This page is about a different car, the 2021 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.

The Intrusion Transceiver Module (ITM) controls all of the added features of the premium version of the Vehicle Theft Alarm (VTA). The ITM adds personal property theft protection by detecting movement within the interior of the vehicle. The microcontroller within the ITM contains motion detection logic, uses On-Board Diagnostics (OBD) and also communicates with other electronic modules in the vehicle as well as with a diagnostic scan tool over the Controller Area Network - Interior High Speed (CAN-IHS) data bus. This method of communication is used by the ITM to communicate with the Body Control Module (BCM) and the Instrument Panel Cluster (IPC).

The ITM receives battery current on a fused B+ circuit through a fuse in the Power Distribution Center (PDC) and is grounded at all times through a take out and connector of the body wire harness that is secured to the body sheet metal at a remote ground point. These connections allow the ITM to remain operational, regardless of the status of the ignition switch. The ITM receives an electronic arm request message from the BCM over the CAN-IHS data bus whenever the VTA is armed. However, the ITM features may be disarmed by the customer by pressing and releasing the Lock button of the Remote Keyless Entry (RKE) FOB with Integrated Key (FOBIK) transmitter three additional times during the 16 second pre-arm period of the VTA, while the security indicator in the IC is still flashing rapidly.

While the VTA is armed, the ITM generates ultra high frequency sound bursts into the vehicle interior through ultrasonic transmit transducers and monitors the return signal input through ultrasonic receive transducers. The transducers are integral to the intrusion module sensors. The ITM logic uses an algorithm to detect movement in the vehicle interior through modulation of the ultrasonic echo that occurs due to the Doppler effect. If interior movement is detected, the ITM sends electronic alarm request messages to the BCM and the IPC over the CAN-IHS data bus to invoke the VTA visual and audible alerts. Vehicle operators must be made aware that items in the vehicle that could move or sway due to environmental conditions or external vibrations may cause nuisance or phantom alarm events.

The ITM microcontroller continuously monitors inputs from the intrusion module sensors as well as from the IPC and the BCM. The ITM monitors the current draw to detect problems with the intrusion module sensors and circuits. The ITM sets active and stored Diagnostic Trouble Codes (DTC) for any monitored system faults it detects.

The hardwired circuits of the ITM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the ITM or the electronic controls and communication between modules and other devices that provide some features of the VTA. The most reliable, efficient and accurate means to diagnose the ITM or the electronic controls and communication related to VTA operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.