Tech Stuff

TPMS tips:Identifying types, applications, functions and service

Shown here is an array of caps intended for TPMS applications. In this photo, notice that the two caps on the right look like metal. The second cap from the right is a chrome-plated plastic and the cap on the far right is a chrome-plated aluminum cap.
<p>Shown here is an array of caps intended for TPMS applications. In this photo, notice that the two caps on the right look like metal. The second cap from the right is a chrome-plated plastic and the cap on the far right is a chrome-plated aluminum cap.</p>

Every vehicle from 2008 model year to the present is equipped with a tire pressure monitoring system (TPMS). If you service tires, you’ll be forced to deal with TPMS. That means that you must invest in a TPMS tool (preferably a combination tool that allows scanning/diagnostics, activating, programming if needed and relearning).

However, it doesn’t stop there. In addition, you must also have the appropriate mechanical tools that are dedicated specifically to TPMS (calibrated torque wrench for hex nuts, calibrated torque wrench for stem installation and for core installation), and rubber grommet install and remove tools; as well as an assortment of service kits (stems, hex nuts, caps, cores, grommets and seals).

There’s no way around this. Either you’re in the TPMS business or you’re not (and if you sell and/or service tires, you are in the TPMS business).

Pay attention to materials

If you’re dealing with aluminum TPMS valve stems, pay attention to the valve cores and caps. Aluminum stems and cores are nickel plated to avoid galvanic corrosion issues. Don’t just toss any core into an aluminum TPMS stem. The same goes for caps — to avoid corrosion issues, you cannot thread-on just any valve cap that’s lying around the shop onto a tire pressure sensor. Don’t use a metal cap, as this can corrode and in most cases not be removable from the aluminum stem. Some aftermarket caps in particular may be made entirely of steel or stainless steel, or they may have a dissimilar metal (female thread) insert encased in plastic.

Here’s an example of galvanic corrosion caused by installing a dissimilar metal cap onto an aluminum valve stem.
<p>Here&rsquo;s an example of galvanic corrosion caused by installing a dissimilar metal cap onto an aluminum valve stem.</p>

Galvanic corrosion can occur when dissimilar metals join, so threading a dissimilar metal cap or metal-insert cap onto the sensor’s stem can result in the cap binding to the stem, making it difficult to remove in the future. If this happens, force may be required to remove the cap that can result in breaking the sensor’s valve stem. This problem is becoming more apparent as the number of vehicles equipped with TPMS increases, and as more owners tend to “enhance” the wheels’ appearance by getting rid of “the ugly plastic caps” and installing chrome-like caps, or when an unwitting DIYer or technician previously installed a non-TPMS cap. If the cap is made of metal and you’re not sure of the base material, don’t use it.

According to Tyson Boyer at Dill Air Controls Products, this is a major concern, but also presents the service provider with an opportunity to educate the customer.

“If you don’t include TPMS in your inspection process and empower your team to properly inspect every vehicle, you are significantly increasing your risk of presenting the unwanted result versus sharing the findings. Corrosion has created technician resistance toward servicing aluminum valve stems. To aid in stronger acceptance and to do what’s right for the customer and your business, we have developed a corrosion-free valve stem. By using an electrolytic process, we were able to chrome-plate a brass cap/stem, which will be available for use with the REDI-Sensor this summer.”

As noted by the TPMS division of JohnDow Industries, there are many different OEM sensors on the market today but there are only two styles of sensors.

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