Tire Pressure Monitoring System

The Tire Pressure Monitor (TPM) system alerts driver when a large change in pressure of one tire exists while vehicle is being driven. TPM system uses Electronic Brake Control Module (EBCM), Anti-lock Brake System (ABS) wheel speed sensor inputs, Class 2 serial data circuit and Instrument Panel Cluster (IPC) to perform system functions. EBCM contains software to calculate relative tire pressure differences. Software requires approximately 30 minutes of straight line driving in three different speed ranges to complete calibration process for detecting a tire pressure condition. Speed ranges are as follows:

• 15-40 MPH
• 40-70 MPH
• 70-90 MPH

Each speed range has two modes of tire pressure detection. EBCM learns tire pressure calibration for each speed range independently. In Monitor Mode 1, EBCM has only partially learned tire pressure calibration for speed range and has limited detection capability for a tire pressure condition. In Monitor Mode 2, EBCM has fully learned tire pressure calibration for speed range and has full detection capability for a tire pressure condition. Once TPM system has fully learned tire pressure calibration EBCM monitors ABS wheel speed Sensor inputs, which will all be same as learned calibration if tire pressures stay same. If tire pressure increases or decreases in one tire circumference and radius will change, which causes that wheel speed sensor input to change. EBCM recognizes this change in wheel speed as a tire pressure condition. If pressure in one tire becomes at least 10 PSI (69 kPa) higher or lower than other three EBCM commands IPC to turn on LOW TIRE PRESSURE indicator via a Class 2 serial data circuit. This indicator does not appear if more than one tire is high or low, or if system is not properly calibrated. System does not alert driver to which tire is high or low.