Resetting TPMS System

With the cold weather hitting us, I now have the Low Pressure warning.

Pumped up the tires after driving home (Hot fill) and expected the system to reset.

Read the manual and it says to drive a certain amount of time post-fill (gas station to home may not have been enough). Expected it to be reset this morning but suspect they need to be filled again.

Anything else to reset this warning once pressures are right?

Also, any recommendations on preventing slow leaks during winter? Nitrogen fill perhaps?

Nitrogen serves only to lighten your wallet. It does little for passenger car tires, which are filled with 78% nitrogen right now.

Buy a gauge. A good one. Check tires monthly and remember, PV=nRT, which is true for all gases, including nitrogen, so you'll lose about 1 PSI for every drop of 10 degrees Fahrenheit.

Permeation means that you'll lose about 1 PSI every month through the tire itself. Nitrogen permeates at a very similar rate to oxygen by the way, and you're already at 78% nitrogen.

It's fall. You're going to have to add air fairly often. Don't use crummy gas station compressors with lots of water in them. The principal advantage of nitrogen is its dryness. A good compressor, regularly maintained, produces dry air. That's how you should fill your tires.

Quote:

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Originally Posted by Kiwirst

Anything else to reset this warning once pressures are right?

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99% of the cars I see with the low tire warning on is because the tires are low. You simply need an accurate gauge.

If you're using that gas station inflator gauge, you're trusting a gauge that's been dropped several times a day, abused by morons, and sits outside 100% of the time...

I wouldn't.

I've got one of these in every car (and one in my tool box): https://www.amazon.com/Accutire-MS-4...pressure+gauge

I use my own compressor, that provides dry air, with an accurate, carefully maintained, inflator....

Cycle the off/on a couple of times
Mine usually resets within a block or two

Thanks for the advice, looks like with the warm up yesterday it finally reset.

I will be picking up an accurate gauge for my compressor for future fixing.

Indirect TPMS vs. Sensor TPMS
Attachment 9168
My 2015.5 XC70 T6 (bought used) came with the "Tire Monitor" system (indirect TPMS) -- this flavor of TPMS does not have a pressure-sensor in the wheel. Rather, it uses the wheel speed sensors, looking for faster rotation of the wheel. Tire circumference shrinks slightly with loss of pressure, therefore has to revolve faster to go the same distance. Volvo claims the indirect system can spot a single tire going soft. But, if two tires are going soft, it reports a "low tire pressure" non-specific to tire location (all 4 tires go yellow in the graphic). When you top-off pressure after a warning comes on, you have to go into MyCar / Tire Pressure, and ask to Recalibrate (only enabled when the car is parked). You have to drive a short distance for the recalibration to complete.

These features lead to some speculation on my part as to how the software detects a lone low-pressure tire. However, I'd rather have someone comment who has tested the indirect system extensively with a calibrated digital pressure gauge, or has insider info on the software algorithm.

Sensor-based TPMS
Attachment 9169
This system has a pressure sensor module (battery-powered) in the filler stem of each wheel. Each sensor has a unique ID code, and radio-broadcasts a pairing of ID + pressure reading, picked up by a common TPMS receiver. When first installed, each ID must be associated with its 1 of 4 tire locations -- done at the factory. The battery is known to last about 10 years (shorter based on climate?). There is no way to replace just the battery. When the TPMS modules are replaced with a set of new tires, there is a recoding step. Dealers can do this recoding. Tire center consultants "will try" to do this, but no guarantees.

A set of 4 new TPMS modules/stems can be purchased as a set cheaper than buying 4 individually -- the set is p/n 31414189, about $250 (VolvoWholesaleOEMParts.com).

There is a way to replace the battery.
Some sensors can be opened to replace the battery, others have to be cut open.
You can find video's on Youtube.

Quote:

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Originally Posted by Willy

There is a way to replace the battery.
Some sensors can be opened to replace the battery, others have to be cut open.
You can find video's on Youtube.

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Sew it up good and tight. The G force on the TPMS module cruising at 125km/hr, or 75 mph is about 300 Gs (300 X the force of gravity).
Don't know whether the casing must be pressure-sealed for it to work....good luck.