Tire Pressure Monitoring

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), ABS wheel speed sensor inputs, Class 2 serial data circuit and Driver Information Center (DIC) to perform system functions. EBCM contains software to calculate relative tire pressure differences. Software requires approximately 30 minutes of straight line driving in each of three speed ranges to complete calibration process and have full capability of detecting a tire pressure fault. Speed ranges are:

• 15-40 MPH (24-64 km/h)
• 40-70 MPH (64-113 km/h)
• 70-90 MPH (113-145 km/h)

EBCM learns tire pressure calibration for each speed range independently. There are two Monitor Modes. In Monitor Mode 1, EBCM has only partially learned tire pressure calibration for speed range, and has limited detection capability for a tire pressure fault. In Monitor Mode 2, EBCM has fully learned tire pressure calibration for speed range, and has full detection capability for a tire pressure fault. Once TPM system has 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 pressure increases or decreases in one tire, tire circumference and radius changes, which causes that wheel speed sensor input to change. EBCM recognizes this change in wheel speed as a tire pressure fault. If pressure in one tire becomes at least 10 PSI (69 kPa) higher or lower than other three, EBCM commands DIC to display LOW TIRE PRESSURE warning message via a Class 2 serial data circuit. This message 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. When tire pressures are at specified PSI, TIRE PRESSURE NORMAL message is displayed when selected on DIC.