TMP Frequently Asked Questions (FAQs)
TPM Frequently Asked Questions (FAQs)The following are some of the most asked questions:
Q: What is a Tire Pressure Monitoring System?
A: The TPM system consists of four sensors (one in each wheel), which transmit wireless (RF) signals to a vehicle receiver (typically, the same receiver that performs the keyless entry function), the Low Tire telltale, and the Driver Information Center (if equipped).
Q: Do all Vehicles Have Tire Pressure Monitoring?
A: Starting with the 2008 MY, all GM vehicles sold in the United States are equipped with tire pressure monitoring, to meet the mandates of FMVSS 138. Some vehicles built prior to the 2008 model year or sold in Canada have tire pressure monitoring; check vehicle build and RPO information to be sure.
Q: What does the Low Tire Telltale Look Like?
A: The Low Tire telltale is a yellow telltale that looks like an exclamation point inside of a horseshoe:
Q: When does the Low Tire Telltale Come On?
A: The Low Tire telltale MUST come on when a tire's pressure drops to 75% of the Recommended Cold Inflation pressure (the pressure value printed on the vehicle placard - the yellow and white sticker in the driver door opening.)
There are several events that may cause a Low Tire warning:
- 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.
- On vehicles where a different placard pressure is required between the front and the rear axles, the tires may have been rotated, pressures adjusted, and the new tire positions were NOT re-learned into the vehicle.
- 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, please refer to bulletin:
- #05-03-10-003E - Low Tire Pressure, Leaking Cast Aluminum Wheels (Repair with Adhesive Sealant)
- #04-03-10-001E - Info - Tire Puncture Repair Procedures for all Cars and Light Duty Trucks
Q: What does the TPMS Malfunction Warning Look Like?
A: The TPMS Malfunction indicator uses the same telltale as the Low Tire warning. The telltale will flash for the first 60 seconds of a KEY ON event, and then go on solid.
Q: How can I tell the difference between a Low Tire and a system malfunction?
A:
- A Low Tire telltale will be on solid immediately after KEY ON, and will be accompanied by a CHECK TIRE PRESSURE message in the Driver Information Center (if equipped).
- A system malfunction causes the telltale to flash for the first 60 seconds of a KEY ON event, and then go solid.
Tip
These behaviors repeat at each KEY ON cycle. The best way to diagnose the vehicle (if you're not sure which warning is being displayed) is to KEY OFF and KEY ON again while watching the telltale and DIC messages.
Q: When are Diagnostic Trouble Codes Reported?
A: DTC's are reported ONLY when there is a system malfunction (flashing telltale). When a Low Tire (solid telltale) is displayed, that means that the system is working exactly as it's designed to do - since there's no malfunction, there is no need for a DTC.
Q: What service is needed if the Low Tire telltale is on?
A: When a vehicle comes in with a Low Tire warning, the tires should be checked for any leaks or damage (from road hazards). After those have been repaired (or if none are found), the tires should be inflated to the pressure shown on the Vehicle Placard - the yellow and white sticker in the driver door opening. It is not necessary to relearn the sensors after correcting the pressure.
Q: Can Tire Pressure Monitoring be turned off?
A: Tire Pressure Monitoring is now a mandated safety system in the United States and cannot knowingly be disabled by an OEM nor an aftermarket service provider (49 USC 30101).
Q: Can the Tire Type and/or Placard Value be changed, if aftermarket tires or wheels are installed?
A: The Tire Type (P Metric, LT Load Range C/D/E) and the Placard Value (Front Placard and Rear Placard, individually) are stored in the receiver as calibrations and CAN be revised at a GM Dealership with a Tech 2. (The RCDLR Setup screens allow this.) Since the under-inflation threshold is calculated as a percentage of the placard; correcting the placard values when different tires are installed will bring the vehicle back into compliance.
Q: What is Sensor Learning (Sensor Re-Learning, Sensor Training, Sensor Matching)?
A: Each sensor has its own unique identification code (ID) that is transmitted as part of its wireless signal. The receiver stores and uses these IDs to determine which sensors are installed on the vehicle, and in which corner of the vehicle the sensor resides in (so that both the pressure information provided in the Driver Information Center and the diagnostics are correct). Sensor Learning is the process that puts sensor ID information into the receiver.
Q: When is Sensor Learning required?
A: Sensor Learning should be done when the vehicle's tires are rotated (since sensor position on the vehicle has changed) or when a sensor is replaced/a new sensor is installed (since a new ID has been introduced to the vehicle). Sensor Learning is not required when simply correcting the tire pressure resolves the vehicle problem.
Q: Why are dashes (" - - "), or a pressure value of 148 PSI (1020 kPa), sometimes displayed after a battery disconnect?
A: These displays come up after a battery disconnect/reconnect because the system is waiting for updated pressure information to be sent from the tire pressure sensors. As each sensor transmits its information, the display is updated appropriately. Note that when dashes or 148 PSI (1020 kPa) are displayed after a battery disconnect/reconnect, the System Malfunction warning is NOT displayed - because the system is still working properly, and simply waiting for updated information from the sensors. Driving the vehicle above 20 mph (32 km/h) for 2 minutes gets the sensors talking, and restores the correct pressure values to the display. It is also possible to restore the values by using the J-46079 TPM tool, using the "Activate" function at each tire to activate the sensor (it is NOT necessary to put the system into Learn mode, in this special case).
Q: Is there a sensor installed in the spare tire?
A: No - a sensor is not installed in the spare tire.
Q: Are all of the sensors the same?
A: All of the sensors are not the same. They are supplied by different manufacturers, and send different RF signals to the vehicle. SOME of the sensors are interchangeable, though - while they may look different, they DO send the same RF signal to the vehicle and MAY be used in place of one another on a vehicle. See the Sensor Information Guide for more details about which parts are interchangeable.
Q: What size is the sensor nut?
A: The sensor uses an 11 mm hex nut for attachment.
Q: Will a tire pressure sensor fit in every wheel?
A: GM wheels (including Accessory Wheels available from GM SPO) are designed to accommodate tire pressure sensors. Many aftermarket wheels also accommodate tire pressure sensors, but not all do. In some, the valve stem hole is placed in such a way (pointing straight into the middle of the wheel, for example) that the motion detection components inside the sensor will not work correctly.
Q: Can the valve core be replaced?
A: The valve core can and should be replaced if it is removed from the sensor, but the replacement part depends on the material of the valve stem (Refer to Service Bulletin # 08-03-10-005). Sensors with a rubber valve stem may use a standard brass valve core for replacement. Sensors with an aluminum valve stem CANNOT use a brass core; instead, they require a nickel-plated valve core to protect against the corrosion that forms when dissimilar metals come in contact. See the service parts guide for the correct GM part numbers to order and use.
Q: Can the grommet (and washer) be replaced?
A: The grommet (and washer) can and should be replaced if the sensor is removed from the wheel. The rubber grommet provides the air seal in the valve stem opening, and a new one should be used to ensure a fresh seal after each service. See the service parts guide for the correct GM part numbers to order and use.
Q: Can the rubber valve stem be replaced by itself?
A: The rubber valve stem is attached to the sensor electronics by a TORX screw. The valve can and should be replaced whenever the sensor is removed from the wheel. See the service parts guide for the correct GM part numbers to use.
Q: Can the sensor be cleaned with a sharp pin?
A: NEVER use a sharp object to clean the pressure port of the sensor; it can be damaged and lead to part failure. If the dirt/grime/obstruction cannot be removed with a cloth, replace the sensor.
Q: How long will the sensor's battery work?
A: The sensor is designed to last for 10 years or 150,000 miles (240,000 kilometers).
Q: Are tire pressure sensors compatible with aftermarket tire sealants?
A: Tire pressure sensors are not compatible with commercially-available tire sealants. Tire sealant materials can clog the pressure port of the sensor, and lead to inaccurate pressure readings and improper Low Tire warnings. Additionally, some sealant products use materials that can degrade the protective potting material that covers the sensor's electronics.
Q: Are tire pressure sensors compatible with GM Inflator Kits?
A: While tire pressure sensors are NOT compatible with commercially-available sealants, they HAVE been tested and ARE compatible with GM Inflator Kits and the sealant that they use. After inflator kit use, the sensor should be inspected for any damage, and replaced/cleaned as needed.
Q: Are tire pressure sensors compatible with nitrogen inflation?
A: Tire pressure sensors are compatible with nitrogen inflation (normal air is already 78% nitrogen).
Q: How do changing outside temperatures affect tire pressure?
A: All gases change pressure as their temperature changes, and air or nitrogen are no exceptions. A good rule of thumb is that tire pressure will change by about 1 psi (7 kPa) when temperature changes by 10° F (6°C). Customers may experience this as temperatures change from summer to fall and into winter - tire pressures will drop as the outside temperature gets colder. Customers may also experience this as temperatures change between mid-day and overnight.
Q: How should tire pressures be set at PDI?
A: Tire pressure should be set to the specified placard pressure at the lowest seasonal temperature the vehicle will see during operation. The correct action to avoid a CHECK TIRE PRESSURE message due to extreme temperature changes is to: Use an accurate high quality tire pressure gauge. Let the vehicle sit and adjust tire pressure to the specified value when tire temperature is at the lowest expected temperature. Never set tire pressure below the placard value regardless of tire temperature or ambient temperature On extremely cold days, if setting tire pressure when the vehicle has been indoors, it may be necessary to compensate for the low external temperature by adding 3-4 psi (21-27 kPa) more than the placard pressure. When convenient, at some later time, when the tires are cold (outdoors), the pressure should be re-checked and adjusted to placard if necessary.
Q: When will the J-46079 tool be updated?
A: TPM Software Version 3.5 has recently been shipped to each GM dealership in the J 46079-30 TPM update kit. This update consists of two parts:
- A hardware update kit which consists of a custom rechargeable battery pack, battery cover with charging terminals, and a charging cradle with a smart charger where the whole tool will fit into the cradle for charging (same concept as a cordless phone). This hardware update substantially increases the life of the batteries and will assure that the TPM Tester always has full battery capacity.
- The software update will add new vehicles and also improve the speed of the tool's read-back ability and accuracy. Sensor transmission signal strength is displayed in the upper left corner of the main display next to the tool's battery level display. When the tool is used in both activate or scan mode, it will receive the sensor's transmission and indicate its signal strength. It is important to note the sensor's transmission signal strength since it is a good indication of an accurate diagnostic.
Q: Where should the J-46079 tool be positioned when it is being used?
A: Tool User Tip: The placement of the TPM Tester's antenna when activating a sensor is critical, especially with the latest software update. When activating a sensor, the antenna tip of the TPM Test J 46079 must be placed on the sidewall, perpendicular to the tire, and close to the valve stem. This will assure proper activation of the sensor. If the antenna of the TPM Tester is placed either on the valve stem or on the wheel itself, the tool may not properly activate the sensor, causing improper diagnosis.