1999 Pontiac Grand Am Owner's Manual - Page 259

yellowblue After the system has learned tire pressures with properly inflated tires, the CHECK TIRE PRESSURE light 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 at less than 15 mph (25 km/h), faster than 75 mph (120 km/h), on rough roads or during turns. The light may also come on if you are driving on partially cleared pavement. 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" in the Index. If the anti-lock brake system warning light comes on, the tire pressure monitor system may not be working. See your dealer for service. (Also, see "Anti-Lock Brake System Warning Light" in the Index). When the CHECK TIRE PRESSURE light comes on, you should stop as soon as you can and check all your tires for damage. (If a tire is flat, see "If a Tire Goes Flat" in the Index.) Also check the tire pressure in all four tires as soon as you can. See "Inflation - Tire Pressure" in the Index. The light will come on and stay on until you turn off the ignition or press the RESET button. Don't reset the tire pressure monitor system without first correcting the cause of the problem and checking and adjusting the pressure in all four tires. If you reset the system when the tire pressures are incorrect, the system will not work properly and may not alert you when a tire is low. 6-37