With Tire Pressure Monitor systems (TPM) being installed on nearly all new vehicles, here are some timely service and care tips. Follow the proper procedures when handling these sensors.

Damage

Analysis of returned sensors indicates physical damage due to improper installation, over- or under-torque of the valve core, and damage to the schrader stem from inflation air chucks or when using tire changers.

A TPM sensor may need to be replaced for multiple reasons: wheel replacement, faulty sensor, faulty schrader valve, or valve damage.

When removing a sensor from a wheel assembly, make certain that the threads of the stem are in good condition.

Inspect the stem for cracks or any indication of a bend, as this could cause a leaking valve.

When removing the valve stem core, use the proper core removal tool.

When installing a TPM sensor, it is critical to use the correct installation torque for the valve stem. A stem or core can be damaged both by over- or under-torquing. Calibrated torque wrenches are available for both the stem nut and the valve core.

The TPMS Service Tool Kit JSP-96254 (fig. 3) is available through the GM Tech Tools program. 1.800.GMTOOLS (1.800.468.6657) or www.gmtechtool.com. The valve stem torque wrench is included in the kit. The valve core torque wrench LIS-18810 is included in the kit and is also available separately.

Over-torquing the core, using a convenional core wrench, can crack the stem housing, which compromises the seal and creates a leaking stem.

The GM torque specification for valve cores is 4 in lb (0.45 Nm). This torque ensures that the core has seated properly in the stem and is properly sealed, without being over-torqued.

It is also important to avoid applying lateral pressure to the head of the valve stem with the air chuck while inflating tires. Excessive lateral pressure can cause the stem to crack or break off, or cause the core to become damaged and begin to leak.

Be extra careful because these stems are made of aluminum and are fastened solidly to the wheel. They are not as flexible as a regular rubber valve stem and cannot absorb the lateral pressure.

Excessive pressure can also be caused by a tire changing event were the changer mount head or tire lever strikes the valve stem.