For 1990-2009 cars

### Tire Pressure Monitoring System Operation

The tire pressure monitor system warns the driver when a significant loss, or gain of tire pressure occurs in any of the 4 tires and allows the driver to display the individual tire pressures and their locations on the driver information center.

The system uses the body control module (BCM), driver information center, instrument cluster, remote function receiver module, a radio frequency transmitting pressure sensor in each tire assembly, and the serial data circuit to perform the system functions. Each sensor has an internal power supply.

When the vehicle is stationary, the sensors internal accelerometer is inactive, which puts the sensors into a stationary state. In this state the sensors sample tire pressure once every 30 s and do not transmit at all if the tire pressure does not change. As vehicle speed increases, centrifugal force activates the sensors internal accelerometer causing the sensors to go into rolling mode. In this mode, the sensors sample tire pressure once every 30 s and transmit in rolling mode once every 60 s. The remote function receiver module receives the data and send it to the BCM, contained in each sensors frequence transmission into sensor presence, sensor mode, and tire pressure. The BCM sends the tire pressure and tire location data to the instrument cluster and the driver information center via the serial data circuit where they are displayed.

The sensors continuously compare their last pressure sample to their current pressure sample and will transmit in re-measure mode if a 8.3 kPa (1.2 PSI) change in tire pressure has been detected in either a stationary or rolling state. When the tire pressure system detects a significant loss, or gain of tire pressure, the tire pressure monitor indicator icon is illuminated on the instrument cluster and if equipped, a check tire pressure type message is displayed on the driver information center.

Both the indicator icon and driver information center message can be cleared by adjusting the tire pressures to the recommended kPa/psi and driving the vehicle above 40 km/h (25 MPH) for at least 2 min.

If power is disconnected from the BCM or if the vehicle battery is disconnected each tire pressure sensor ID is retained but all of the tire pressure information is lost. Under these circumstances the BCM cannot assume that the tire pressures were maintained over an unknown period of time. If equipped, the driver information center will display all dashes and the scan tool will indicate a default tire pressure value of 1 020 kPa (148 PSI) for each tire. Driving the vehicle above 40 km/h (25 MPH) for at least 2 min. will activate the sensors causing the driver information center to display the current tire pressures.

The BCM has the ability to detect malfunctions within the tire pressure monitor system. In the event a DTC is set, the tire pressure monitor indicator icon on the instrument cluster will flash for 1 min. and then remain illuminated after the ignition is turned ON and the instrument cluster bulb check has been completed. Any malfunction detected will cause the driver information center to display a service tire monitor system type message.

### Auto Learn Functionality

Auto learn functionality. In addition to the sensors signal, the tire pressure monitor system also receives the left/right information sent by the sensors. This information is determined by the rotating direction of the tire. The tire pressure monitor system decides if the tire which is sending information is located at the front or rear axle. It can determine that information by the sensors signal strength. This process takes about 3-9 min. of driving.