2008 Saturn Astra Owner's Manual - Page 240

9-50 Vehicle Service and Care The low tire pressure warning light comes on at each ignition cycle until the tires are inflated to the correct inflation pressure. The low tire pressure warning light may come on in cool weather when the vehicle is first started, and then turn off as you start to drive. This could be an early indicator that the air pressure in the tire(s) are getting low and need to be inflated to the proper pressure. You must begin driving before the TPMS system is operational. TPMS sensors need to be installed onto the full-size tire and wheel assemblies, and the tires adjusted to the manufacturers' recommended tire pressure amount. A Tire and Load Information label is attached to the vehicle, and shows the size of the vehicle's original equipment tires and the correct inflation pressure for the tires when they are cold. See Loading the Vehicle on page 8-30, for an example of the Tire and Load Information label and its location on the vehicle. Also see Inflation - Tire Pressure on page 9-46. The vehicle's TPMS can warn you about a low tire pressure condition but it does not replace normal tire maintenance. See Tire Inspection and Rotation on page 9-51 and Tires on page 9-38. Notice: Liquid tire sealants could damage the Tire Pressure Monitor System (TPMS) sensors. Sensor damage caused by using a tire sealant is not covered by your warranty. Do not use liquid tire sealants. Each TPMS sensor has a unique identification code. Any time you replace one or more of the TPMS sensors or rotate the vehicle's tires, the identification codes are automatically learned by the TPMS. This occurs within a few moments of driving the vehicle over 19 mph (31 km/h). Tire Pressure Monitor Operation The Tire Pressure Monitor System (TPMS) is designed to warn the driver when a low tire pressure condition exists. TPMS sensors are mounted onto each tire and wheel assembly, excluding the spare tire. The TPMS sensors monitor the air pressure in the vehicle's tires and transmit tire pressure readings to a receiver located in the vehicle. When a low tire pressure condition is detected, the TPMS illuminates the low tire pressure warning light located in the instrument panel cluster.