ONSTAR | VEHICLE DIAGNOSTICS | DIAGNOSTICS INFO

Using data retrieved from your Tire Pressure Monitoring System, we'll let you know in your OnStar Vehicle Diagnostics* report if your tire pressure needs attention. You should check your tires monthly, at a time when you haven't driven for at least three hours.

What is the Tire Pressure Monitoring System and how does it work?
Tire Pressure Monitoring System — If your vehicle is equipped with a Tire Pressure Monitor System (TPMS), it uses radio and sensor technology to check tire pressure levels in each of your installed tires. TPMS sensors monitor the air pressure in your vehicle's tires and transmit tire pressure readings to a receiver located in the vehicle. The TPMS is designed to alert the driver if a low tire pressure condition exists, and may also allow the driver to check tire pressure levels using the Driver Information Center (DIC) on your dashboard. If you have replaced your factory-installed tires or wheels, your TPM system may not be functioning properly. Check with your installer for compatibility.
Tire Pressure and Changing Temperatures — Tire pressure can change over time as temperature changes. The pressure goes up as temperature goes up, and pressure goes down as temperature goes down. (A good rule of thumb is that tire pressure changes 1 psi for a change of 10°F.) This can happen seasonally (from summer into fall), daily (from a cold night to a warmer afternoon), and while driving (the tires warm up as you drive).
You may notice during cooler weather conditions that the Low Tire Pressure indicator will appear when the vehicle is first started and then turn off as you start to drive. This is an early indicator that the pressure is getting low and tires need to be inflated to the proper pressure.
What does the telltale indicator (horseshoe-like symbol with an exclamation point) in my vehicle mean?
When Your Vehicle Telltale Is On Continuously — One or more of your tires may be significantly under-inflated and require attention. Check your tire pressures as soon as possible. Correcting the tire pressures will cause this light to go out (much like adding fuel to your vehicle causes your yellow Low Fuel light to go out.)
When Your Vehicle Telltale Flashes, and Then Is On Continuously — You may have a problem with your Tire Pressure Monitoring System. See your dealer for service.
If you have replaced your factory-installed tires or wheels, your TPM system may not be functioning properly. Check with your installer for compatibility.

How do I read the tire pressure alerts in my OnStar Vehicle Diagnostics report?

Each month, OnStar retrieves information from the Tire Pressure Monitoring System in your vehicle and details it in your OnStar Vehicle Diagnostics report. Since OnStar cannot confirm that these readings are always from a "cold" tire, you may see variation from month to month in your readings, and you should confirm pressures on each tire before adjusting them.

If we detect a tire pressure reading that is outside of the manufacturer's recommended range, the tire status will be changed from green to yellow or red.

Please note: Sometimes, the same tire pressure value will show up as different color-coded alerts for different tires in your email report. This happens when values are rounded off to the nearest PSI. If these different color alerts appear in your email, you should also check the actual pressure for both tires.

Status:	Diagnostic:	Action:
	Tire Pressure Monitoring: Normal	No maintenance needed. Your tires are inflated in the proper range to ensure optimum performance and fuel economy.
	Tire Pressure Monitoring: Low	One or more of your tires may need attention. At your next fuel fill-up, check all your tires for proper inflation. Underinflated tires can cause: Premature or irregular wear Poor handling Reduced fuel economy
	Tire Pressure Monitoring: --	This information may be missing due to a communications error that prevented OnStar from retrieving your tire pressure data. If there is a message in your Digital Information Center to 'service tire pressure monitoring system', then you cannot rely on tire pressure monitoring or the OnStar system to alert you that your tires are improperly inflated. The cause of this situation could be: The factory-installed wheels have been replaced with wheels that do not have compatible sensors. The pressure sensors in your factory installed wheels are not functioning properly. Refer to your owner's manual for further information.
	Tire Pressure Monitoring: Low	One or more of your tires requires immediate attention to ensure safe vehicle operation. Please check all your tires for proper inflation as soon as possible. Underinflated tires can cause: Premature or irregular wear Tire failure Poor handling Reduced fuel economy
	Tire Pressure Monitoring: High	One or more of your tires requires immediate attention to ensure safe vehicle operation. Please check all your tires for proper inflation as soon as possible. Overinflated tires can cause: Unusual wear Poor handling Rough ride

How do I check my tire pressure?
Checking Your Tires — Tire pressure should be checked monthly and should only be adjusted on cold tires (when your vehicle has been parked for at least three hours or driven less than one mile).

Tire pressure information can be found on the tire placard, which is located on the pillar of the driver's door. Do NOT inflate the tires to the pressure value shown on your tire sidewall - that value is the maximum inflation pressure for the tire. Your tire pressures should match the Cold Inflation Pressure shown on the tire placard inside your front driver's door pillar.

Use a good-quality gauge to check tire pressure. You cannot tell if your tires are properly inflated simply by looking at them. Radial tires may look properly inflated even when they're underinflated.

Remove the valve cap from the tire valve stem. Press the tire gauge firmly onto the valve to get a pressure measurement. If the inflation pressure matches the Cold Tire Pressure on the tire placard, 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 until you reach the recommended amount. Recheck the tire pressure with the tire gauge. Be sure to put the valve caps back on the valve stems. They help prevent leaks by keeping out dirt and moisture. As always, refer to your vehicle's owner's manual for more detailed information on tire maintenance.
What should I do after a tire rotation?
Rotating Your Tires — If you rotate your own tires or have them serviced at a facility that is not an authorized GM repair center, you should make sure that the tire pressure sensors are reset as outlined in your owner's guide. This will ensure that the sensors in each tire represent the new tire positions. If this procedure is not followed, it is likely that the readings in your OnStar Vehicle Diagnostics email and on the display in your vehicle may indicate the incorrect tire locations.
How does tire pressure relate to fuel economy?
Tire Pressure and Fuel Economy — Keeping your tires properly inflated can help save up to 3.3%^† on gas mileage. Every 1 psi drop in pressure for all tires lowers your vehicle's gas mileage by 0.4%.

*Available on 2004 MY & newer GM models equipped with the GM Oil Life System. Diagnostics not available on Pontiac Vibe, Saab 9-3 and 9-5. Diagnostic services vary on Cadillac SRX V8, Saturn VUE, Ion and L-Series, Chevy Silverado diesel and GMC Sierra diesel. For details, call 1.888.4.ONSTAR (1.888.466.7827) or press your blue button.

^†fueleconomy.com

IMPORTANT INFORMATION OnStar services require vehicle electrical system (including battery), wireless service and GPS satellite signals to be available and operating for features to function properly. Subscription Service Agreement required. The U.S. Federal Communications Commission (FCC) ruled that wireless carriers will no longer be required to support the analog wireless network beginning in 2008. As of January 1, 2008, OnStar plans to offer service only through equipment that operates on the digital network, which may require the purchase of a system upgrade for eligible vehicles. Click here for Frequently Asked Questions. Call 1.888.4.ONSTAR (1.888.466.7827) or browse this site for OnStar's Terms and Conditions, Privacy Statement, and system limitations and details. Additional information can be found in the OnStar Owner's Guide.