The tire inflation monitor (TIM) system uses the 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 inflation monitor system functions.
The software requires approximately one half hour of straight line driving to complete the TIM autolearn. There are several speed ranges that the EBCM needs to learn the tire inflation configuration in order to have the full capability of detecting a low tire 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 low tire detection.
| • | Monitor Mode 1 |
| • | Monitor Mode 2 |
The EBCM learns the tire inflation configuration for each speed range independently. In Monitor Mode 1, the EBCM has only partially learned the tire inflation configuration for the speed range and has limited detection capability for a low tire condition. In Monitor Mode 2, the EBCM has fully learned the tire inflation configuration for the speed range and has full detection capability for a low tire condition. If the EBCM is not in Monitor Mode 1 or Monitor Mode 2, a low tire condition cannot be detected because the EBCM has not learned the tire inflation configuration of the vehicle. The EBCM may have fully learned (Monitor Mode 2) the tire inflation configuration in one speed range, but may have partially learned (Monitor Mode 1) or not learned at all the tire inflation configuration in the other speed ranges.
The instrument cluster, through the DIC, performs two functions related to the tire monitoring system.
| • | Displays the warning message CHECK TIRE PRESSURES when commanded by the EBCM, via the class 2 serial data message. |
| • | Sends the tire inflation 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.
Drive Cycle
The electronic brake control module (EBCM) defines a drive cycle as the completion of the EBCM initialization sequence. The EBCM performs the initialization sequence once each ignition cycle. Refer to Initialization Sequence in Antilock Brake System.
