Module, Ultrasonic And Anti-Tilt: Operation

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

The Ultrasonic and Anti-tilt Module (UAM) controls all of the added features of the premium version of the Vehicle Theft Alarm (VTA). The UAM adds personal property theft protection by detecting movement within the interior of the vehicle, provides tire-theft and tow-away protection by monitoring the pitch and roll of the vehicle. The microcontroller within the UAM contains both motion detection and anti-tilt logic and is also a Local Interface Network (LIN) slave node that communicates over the LIN data bus with the Body Control Module (BCM), which is the LIN master node.

The UAM receives battery voltage 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 UAM to remain operational, regardless of the status of the ignition switch. The UAM receives an electronic arm request message from the BCM over the LIN data bus whenever the VTA is armed. However, the UAM features may be disarmed by the customer by pressing and releasing the Lock button of the Remote Keyless Entry (RKE) transmitter three additional times during the 16 second pre-arm period of the VTA, while the security indicator in the Instrument Panel Cluster (IPC) is still flashing rapidly.

While the VTA is armed, the UAM generates ultra high frequency sound bursts into the vehicle interior through an ultrasonic transmit transducer and monitors the return signal input through an ultrasonic receive transducer. The UAM logic uses an algorithm to detect movement in the vehicle interior through modulation of the ultrasonic echo that occurs due to a Doppler effect. The UAM also monitors internal low gravity (also known as low G) accelerometers to detect changes in vehicle pitch and roll. If interior movement or changes in vehicle pitch and roll are detected, the UAM sends electronic alarm request messages to the BCM over the LIN data bus, and the BCM invokes 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 alarms.

The hard-wired circuits of the UAM 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 UAM 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 UAM or the electronic controls and communication related to VTA operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.