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That pesky TPMS

I’ve been reviewing the 800 or so repairs reported over the past quarter, and once again one problem stands out as the most common. Beginning next month, all vehicles will have to be equipped with a standard tire pressure monitoring system (TPMS). Since last year 70 percent of all vehicles have been required to have such a system as standard equipment. Problem is, these system have a high failure rate in many models, including the Nissan Versa. So if you have a problem with the TPMS in your car, you’re far from alone.

If memory serves, the TPMS mandate was a response to a number of fatal 1990s-era Ford Explorer rollovers, many of which were partly caused by underinflated tires. Many people don’t check their tires often enough, especially in this age of self-serve gasoline. So now everyone gets a yellow warning light when a tire needs more air.

TPMSThere are two major types of systems. The more precise solution is a pressure gauge in each wheel that wirelessly communicates with an on-board module. The most sophisticated systems go beyond a warning light to provide the actual pressure reading for each wheel. The cheap solution uses the ABS sensors to compare wheels speeds, in combination with just a pair of direct pressure sensors (in case all four tires are equally underinflated). An underinflated tire has a smaller diameter, and so it rotates faster. Some manufacturers argued for an ultra-cheap system that used only the ABS sensors, and such systems were used in some cars before the mandate went into effect, but the government rejected this as a sufficient solution.

Problem is, in many cars the yellow light comes on–and stays on–even when the tires are properly inflated. When the TPMS isn’t working correctly, sometimes only a system re-set is needed. But other times a sensor or a module must be reprogrammed or even replaced. Currently the former two solutions aren’t counted in TrueDelta’s reported repair trip rates, but the last is.

When all else fails to fix the problem, some people resort to a square of black tape. And, no, that doesn’t count as a successful repair.