The tire pressure monitor (TPM) system is also known as the tire inflation monitor (TIM) system.
The TPM system alerts the driver when a large change in the pressure of one tire exist. The system detects a tire pressure condition while the vehicle is being driven. Once a tire pressure condition is detected, the system alerts the driver that a tire pressure condition exist, whenever the ignition is ON.
The systems warning indicator message appears on the DIC/IPC if the tire pressure in one tire becomes at least 69 kPa (10 psi) lower or higher than the other three tires and the ignition is ON. The warning message does not appear if more than one tire is low or high, or if the system is not calibrated properly. The system does not alert the driver which tire is low or high. To clear this message, set the tire pressures to manufacture's specifications and perform the system reset procedure.
The TPM system uses the electronic brake control module (EBCM), wheel speed sensors, class 2 serial data messages, and instrument cluster in order to perform the system functions.
The EBCM contains the software to perform the system monitoring functions. The EBCM uses wheel speed data obtained from the wheel speed sensors to detect relative pressure differences. Any ABS/TCS system activity causes the EBCM to temporarily suspend the tire pressure monitoring system functions.
The software requires approximately one half hour of straight line driving to complete the TPM autolearn function. There are several speed ranges that the EBCM needs to learn the tire pressure configuration in order to have the full capability of detecting a tire pressure condition. The speed detection ranges are the following:
| • | 24-64 km/h (15-40 mph) |
| • | 64-113 km/h (40-70 mph) |
| • | 113-145 km/h (70-90 mph) |
Each speed range has 2 modes of tire pressure detection:
| • | Monitor Mode 1 |
| • | Monitor Mode 2 |
The EBCM learns the tire pressure configuration for each speed range independently. In Monitor Mode 1, the EBCM has only partially learned the tire pressure configuration for the speed range and has limited detection capability for a tire pressure conditions. In Monitor Mode 2, the EBCM has fully learned the tire pressure configuration for the speed range and has full detection capability for a tire pressure condition. If the EBCM is not in Monitor Mode 1 or Monitor Mode 2, a tire pressure condition cannot be detected because the EBCM has not learned the tire pressure configuration of the vehicle. The EBCM may have fully learned (Monitor Mode 2) the tire pressure configuration in one speed range, but may have partially learned (Monitor Mode 1) or not learned at all the tire pressure configuration in the other speed ranges.
The instrument cluster through the DIC performs two functions related to the tire monitoring system.
| • | The instrument cluster turns on the tire pressure warning indicator on the system monitor when commanded by the EBCM, via the class 2 serial data message. |
| • | Sends the tire pressure monitor system reset command to the EBCM, 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 EBCM and the instrument cluster.
