2004 Chevrolet Impala Owner's Manual - Page 328

When to Check Check your tires once a month or more. Don't forget your compact spare tire. It should be at 60 psi (420 kPa). Tire Pressure Monitor System If your vehicle has the tire pressure monitor system, it can alert you to a large change in the pressure of one tire. The system "learns" the pressure at each tire throughout the operating speed range of your vehicle. The system normally takes between 45 and 90 minutes of driving to learn the tire pressures. This time may be longer depending on your individual driving habits. Learning need not be accumulated during a single trip. Once learned, the system will remember the tire pressures until the system is recalibrated. After the system has learned tire pressures with properly inflated tires, the LOW TIRE PRESSURE message will come on if the pressure in one tire becomes 12 psi (83 kPa) lower than the other three tires. The tire pressure monitor system won't alert you if the pressure in more than one tire is low, if the system is not properly calibrated, or if the vehicle is moving faster than 70 mph (110 km/h). The tire pressure monitor system detects differences in tire rotation speeds that are caused by changes in tire pressure. The system can alert you about a low tire - but it doesn't replace normal tire maintenance. See Tires on page 5-58. How to Check Use a good quality pocket-type gage to check tire pressure. You can't tell if your tires are properly inflated simply by looking at them. Radial tires may look properly inflated even when they're underinflated. Check the tire's inflation pressure when the tires are cold. Cold means your vehicle has been sitting for at least three hours or driven no more than 1 mile (1.6 km). Remove the valve cap from the tire valve stem. Press the tire gage firmly onto the valve to get a pressure measurement. If the cold tire inflation pressure matches the recommended pressure on the Tire and Loading Information label, no further adjustment is necessary. If the inflation pressure is low, add air until you reach the recommended amount. If you overfill the tire, release air by pushing on the metal stem in the center of the tire valve. Recheck the tire pressure with the tire gage. Be sure to put the valve caps back on the valve stems. They help prevent leaks by keeping out dirt and moisture. 5-66