Tire Monitoring System: Description and Operation

Tire Pressure Monitor Description and Operation

The tire pressure monitor (TPM) system warns the driver when a significant loss, or gain of tire pressure occurs in any of the 4 tires and will illuminate the instrument panel cluster (IPC) tire pressure monitor indicator icon at a constant rate after the ignition is turned ON and the IPC bulb check has been completed.

The tire pressure module has the ability to detect malfunctions within the TPM system. In the event a DTC is set, the tire pressure monitor indicator icon on the IPC will flash for 1 minute and then remain illuminated after the ignition is turned ON and the IPC bulb check has been completed.

The system uses the instrument panel cluster (IPC), tire pressure module, and a radio frequency (RF) transmitting pressure sensor in each wheel/tire assembly to perform the system functions. Each sensor has an internal power supply with a 10 year service life.

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 seconds 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 seconds and transmit in rolling mode once every 60 seconds. The tire pressure module receives and translates the data contained in each sensors RF transmission into sensor presence, sensor mode, and tire pressure.

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 TPM system detects a significant loss, or gain of tire pressure, the tire pressure monitor indicator icon is illuminated on the IPC by the tire pressure module. The illuminated indicator icon can be cleared by adjusting the tire pressures to the recommended kPa/psi and driving the vehicle above 32 km/h (20 mph) for at least 2 minutes.