TPMS System Module
WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The SJB contains the TPMS functionality. Refer to TIRE PRESSURE MONITORING SYSTEM in Diagnosis and Testing for TPMS fault diagnosis and repair.
The SJB compares the information of each tire pressure sensor transmission against a pressure limit. If the SJB determines that the tire pressure has fallen below the low limit, the SJB communicates this to the instrument cluster on the vehicle communication bus.