The Tire Pressure Monitoring System (TPMS) on your mid-2007-or-newer vehicle is designated as a safety feature.  Indeed, when operable, it alerts you to a tire pressure drop via a dashboard light representing a cross-section of a tire surrounding an exclamation point.

The NHTSA (National Highway Traffic Safety Administration) concocted the well-intentioned plan for TPMS in 2005 and mandated auto manufacturers to include the system on all vehicles sold in the United States beginning in latter 2007.

Studies showed that many tire failures, along with resulting rollovers and other accidents were rightfully attributed to vehicles running on underinflated tires.  Consumers in general tend to neglect vehicle maintenance including regular tire pressure checks.  So, a light to warn drivers of insufficient tire pressure makes sense from a safety standpoint.

As is typical though, implementation of a viable concept can create unforeseen problems.

I first wrote of TPMS in 2008 when we were all new to the system.  First, many drivers did not recognize the warning light — but that quandary could be solved with an internet search or a quick scan of the owner’s manual.  The subsequent fix of checking pressure and testing for leaks could then ensue as intended by the warning system.

I wrote more columns about TPMS in 2012 — three in fact, to answer the deluge of reader concerns and questions coming in.  The main issue was when vehicle owners headed to their favorite tire shop to install old winter tires already mounted to wheel rims.  Tire shops were forbidden (faced with $10K fine) to install wheels without the electronic sensors incorporated into the tire valves on cars and trucks with TPMS, as it was deemed that such action intentionally rendered the safety system inoperable.

Consumers were shocked when finding that those old wheels could not be installed without retro-fitting sensors to them, which amounted to $200 to $400 additional expense.  This brought to light the problem of non-standardization of the sensors.

This dilemma was not unforeseen.  The tire industry lobbied to have the systems and sensors standardized.  Unfortunately, that did not happen and each manufactured developed systems of their own designs and parts.  They were not only all different from the start, but each auto manufacturer is continually revising their systems to this day.

Each wheel’s sensor contains of a small circuit board capable of sending signals, based on varying software, to a main module when pressure drops.  Again, each system is unique, triggering its warning light based on pressure drops — some at a 15% drop, some at 20% and others at incremental drops in pounds per square inch of pressure.

The sensors also contain a battery, which commonly fails in 8-10 years.  Consumers then face the cost of replacement, just as those who had to retro-fit old wheel rims.  Tire experts believe that standardization would have brought replacement costs down, but as it stands, new ones still run $50-$75 and up per wheel.

The result is that any safety effect becomes moot when many owners elect to simply ignore the illuminated light on the dash rather than incur the expense of sensor replacement.  That behavior is innocuous, other than necessitating periodic manual tire pressure checks.  A lit TPMS light incurs no adverse effects on vehicle operation, but does reduce the value of a used car by at least the amount of new sensors.

Readers may contact Bill Love via e-mail at precisiondriving@spokesman.com.

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