TPMS Reset Tool Relearn Auto Car Tire Pressure Sensor for GM Vehicle 2021 Tire Pressure Monitor Sensor TPMS Activation Tool For vehicles equipped with a 315 or 433 MHz Tire Pressure Monitoring (TPM) system, (BCM), 4 radio frequency transmitting pressure sensors and serial data circuit to perform tire pressure monitoring system read-in mode function. After every tire rotation, BCM replacement, or sensor replacement, a sensor re-read-in procedure must be performed. Once the re-read mode is enabled, the identification code of each sensor will be read into the BCM memory. When a sensor ID is read in, the BCM chirps the horn to indicate that the sensor has sent the ID and the BCM has received and read it. The BCM must read the sensor IDs in the correct sequence to determine the correct sensor location. The first identification code read in is assigned to the left front position, the second to the right front position, the third to the right rear position and the fourth to the left rear position. The turn signals will illuminate individually to indicate the correct sequence of reading positions. Use EL-50448 or equivalent to diagnose sensor function Each sensor has a low frequency coil inside. When Tire Pressure Monitoring is used in active mode, a low frequency transmission signal is generated that activates the sensor. In read-in mode, the sensor responds to low frequency activation by transmitting a signal. In TPM read-in mode, when the BCM receives a read-in mode transmission, it assigns sensor IDs to vehicle locations corresponding to the sequence in which they were read. Sensor function - method using pressure increase/decrease In static mode, each sensor takes a pressure measurement sample every 30 seconds. If the tire pressure increases or decreases by more than 8.3 kPa (1.2 psi) from the last measurement, a remeasurement will be taken immediately to confirm the change in air pressure. If the air pressure does change, the sensor transmits in read mode. In the tire pressure monitor read-in mode, when the BCM receives a read-in mode transmission signal, it assigns the sensor identification code to the position of the vehicle corresponding to its read-in sequence. Cancellation of re-read mode If the ignition switch is turned OFF, or if no sensor is read for more than 2 minutes, the re-read mode will be canceled. If the re-read mode is canceled before the first sensor is read, the original sensor ID will be preserved. If the re-read mode is canceled after the first sensor has been read, the following will happen: All stored sensor IDs will be invalidated in the BCM memory. The driver information center will display a dash instead of tire pressure.