GM Service Manual Online
For 1990-2009 cars only

The tire pressure monitor (TPM) system alerts the driver when a large change in the pressure of one tire exists while the vehicle is being driven. The TPM system uses the electronic brake control module (EBCM), ABS wheel speed sensor inputs, serial data circuit, and the tire pressure warning indicator to perform the system functions. The EBCM contains software to calculate relative tire pressure differences. The software requires approximately 60 minutes or more of driving at a speed of 30 km/h (19 mph) or above to complete the calibration process to have full capability for detecting a tire pressure condition.

Once the TPM system has learned the tire pressure calibration the EBCM monitors the ABS wheel speed sensor inputs, which will all be the same as the learned calibration if the tire pressures stay the same. If the pressure in one tire increases or decreases so too will that tire's circumference and radius, which causes that wheel speed sensor input to change. The EBCM recognizes this change in wheel speed as a tire pressure condition. If the pressure in one tire becomes lower or higher than the other 3, the EBCM commands the tire pressure warning indicator ON. The system does not alert the driver to which tire pressure is high or low. If the tire pressures are at the specified pressure, reset the tire pressure warning indicator, refer to Tire Pressure Monitor Procedure .