Tire Pressure Module: Description and Operation
TPMS SYSTEM MODULEThe smart junction box (SJB) contains the tire pressure monitoring system (TPMS) functionality. The 2 systems have separate diagnosis and testing but they are serviced as one module.
The SJB compares the information of each tire pressure sensor transaxle against a pressure limit. If the SJB determines that the tire pressure has fallen below the low limit (the pressure listed on the vehicle certification label minus 25 percent), the SJB communicates this to the instrument cluster on the vehicle communication bus.