As a rule of thumb, tire pressure will change about 7kPa (1 psi) for every 6°C (10°F) change in temperature – dropping when it gets colder outside and rising when it gets warmer. In the colder winter months, an illuminated Tire Pressure Monitor (TPM) warning light is a more common occurrence. Correcting the tire pressure will usually resolve the issue.
All GM vehicles sold in the U.S. since 2008 have been equipped with a Tire Pressure Monitor System. The system measures tire pressure and, when a tire’s pressure drops to 70% of the recommended cold inflation pressure (listed on the vehicle placard on the driver’s door opening, not the tire sidewall), the TPM warning light will illuminate to warn the driver of a low tire pressure condition.
But what about when the TPM warning light flashes?
Is it an indication of low tire pressure, or is there a TPM system malfunction? With low tire pressure, the warning light on the instrument cluster will stay on solid and no system DTCs will be set. If the warning light flashes, there will be DTCs set, and there is a TPM system condition that needs diagnosis.
Service TPM System
The TPM warning light will flash for about one minute, and a Service Tire Monitor message will be displayed when a system malfunction occurs.
For example, if one or more tire pressure sensors does not transmit information for 18 minutes of driving, the TPM system will set a DTC, display a message on the Driver Information Center (DIC), and the warning light will flash for about a minute, after which the light will stay on solid for the remainder of the ignition cycle.
If the system fault is intermittent, the message/light may also be intermittent.
Low Tire Pressure
If the TPM system detects a tire pressure below the threshold, the Check Tire Pressure message will display on the DIC and the TPM warning light will come on and stay on. The message and light may be intermittent in nature, especially during cold weather.
The current tire pressures can be displayed on the DIC on many GM models.
There are several conditions that will cause the low tire pressure warning message/light to display:
• The tire may have picked up a road hazard and/or have a slow leak.
• The tire pressure may not have been checked in the past six months.
• The air pressure in a cold tire may be at the pressure where the system is required to warn the driver. However, that same tire will rise in temperature and pressure as the customer drives, causing the message and light to go out.
• The tires may have been rotated, pressures adjusted, and the new tire positions were not re-learned to the vehicle. Check for this condition, especially on vehicles that have two different placard pressures for front and rear tires.
• There may be a slow leak in one of the wheel and tire assemblies (Valve Stem, Wheel Rim, or Aluminum Wheel Porosity Leak). If this condition is found, refer to Bulletin #05-03-10-003 – Low Tire Pressure, Leaking Cast Aluminum Wheels and #04-03-10-001 Tire Puncture Repair Procedures for all Cars and Light Duty Trucks.
In order to prevent possible electrostatic discharge damage to the TPM Sensor, technicians should be statically discharged before checking or filling tires.
Keep in mind that improperly adjusted tire pressures also may lead to ride, handling and road noise concerns.
If any of these conditions are present on a vehicle, the first step in diagnosis is to verify that the tires are inflated to the correct pressures.
Driving in Cold Temperatures
Tire pressure should be set to the specified placard pressure at the lowest seasonal temperature the vehicle will encounter during operation.
To help avoid a Check Tire Pressure message due to extreme temperature changes:
• Use an accurate, high quality tire pressure gauge.
• Re-learn the TPM sensors and adjust the tire pressure to the placard values after every tire rotation.
• Let the vehicle sit and adjust the tire pressure to the specified value when the tire temperature is at the lowest expected temperature.
• Never set the tire pressure below the placard value, regardless of tire temperature or ambient temperature.
• When inflating tires, a “cold” tire is one that has been sitting for at least three hours, or driven no more than one mile (1.6 km).
On extremely cold days, if setting the tire pressure when the vehicle has been indoors, it may be necessary to compensate for the low outside temperature by adding 21-27 kPa (3-4 psi) more than the placard pressure.
At a later time, when convenient and when the tires are cold (outdoors), the pressure should be re-checked and adjusted to the placard pressures if necessary.
Using the TPM Tool
The EL-52545 TPMS and RF tool is a valuable aid in diagnosing system faults with TPM systems.
Keep in mind that the tool’s software requires periodic updates in order to function properly on new model vehicles. Failure to update the tool with the latest software version may result in possible misdiagnosis.
When activating a sensor using the TPM tool, the placement of the tool antenna is critical. Place the antenna tip of the TPM tool on the sidewall, perpendicular to the tire, and close to the valve stem.
If the antenna of the TPM tool is placed either on the valve stem or on the wheel itself, the tool may not properly activate the sensor, which may lead to improper diagnosis.
If a sensor does not respond when activated by the tool, try activating another sensor that responded previously to determine if the tool is able to activate the sensor or if there is an issue with one particular sensor.
If the TPM sensors cannot be learned after installation, be sure the wheel assembly has the correct TPM sensors. 2021 and later GM models, including the Tahoe, Suburban, Yukon and Escalade, with the new Vehicle Intelligence Platform (VIP) electrical architecture use a different TPM sensor than vehicles with the earlier Global “A” Architecture electrical system.
Both sensor types use the same sensor body, so they look the same. However, they cannot be interchanged.
Look for the correct identification mark the TPM sensor on VIP models has a “4” on the sensor; non-VIP models have “4C” on the sensor before installing them.
For additional information about TPM System operation, including Frequently Asked Questions that can be shared with customers, refer to Bulletin #07-03-16-004D.