Tire Pressure Monitor System Circuit Description

The tire pressure monitor system is a software driven system. The system uses the existing antilock braking system components (Electronic Brake/Traction Control Module (EBTCM) and wheel speed sensors), class2 serial data line and instrument cluster to perform the system functions.

The EBTCM contains the software to perform the system monitoring functions. The EBTCM uses wheel speed data obtained from the wheel speed sensors to detect relative pressure differences of 10 psi.

This means that one tire is at least 10 psi lower in pressure than the other three. The EBTCM uses only smooth data. Braking, an acceleration or deceleration of greater than 0.19, and/or any ABS/TCS systems activately causes the EBTCM to stop perform tire pressure monitor system functions. When the EBTCM detects a low tire pressure condition the EBTCM sends a message to the instrument cluster via the class 2 serial data line.

The instrument cluster performs two functions related to the tire monitoring system.
^ Displays the warning message TIRE PRESSURE LOW: CHECK TIRES when commanded by the EBTCM, via the class 2 serial data line.
^ Sends the tire pressure monitor system reset command to the EBTCM, via the class 2 serial data line.

The class 2 serial data line is used to send all tire pressure monitor system related information between the EBTCM and the instrument cluster.

To clear the Tire Pressure Monitoring System message perform the following steps:
1. Set all tires to the manufacturer's recommended pressure.
2. Start engine.
3. Press the GAGES button on the I/P until the TIRE PRESSURE message appears on the instrument cluster message center display.
4. Press and hold the RESET button on the I/P until the TIRE PRESSURE RESET message appears.
5. Release the button, the TIRE PRESSURE NORMAL message appears. The system is now in the auto learn mode.