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Re:Solving my truck’s TPMS sensor problem with the help of a... by loeg on Monday August 22, 2022 @02:52PM (#32555583)
Yeah, TPMS can be a real pain in the ass. And the thresholds it has for reporting true-positives are pretty extreme (~25% low), because the auto industry objected to the cost of accurate sensors.

As far as diagnosing and programming at home, I have a handheld OBD-II reader ($35) that can report TPMS codes like this from the car (without a laptop), and also an OBD-II TPM QuickSet ($120) from ATEQ (a more basic model than the shop had). The QuickSet tool is configured over USB, then attaches to ODB-II to write new TPMS codes into the car. It's useful for swapping between summer and winter wheelsets without a shop.

Re:Solving my truck’s TPMS sensor problem with the help of a... by spockz on Monday August 22, 2022 @04:23PM (#32556709)
I’m confused why something is needed. On my Ford I can just “reset” the TPMS after switching wheels from the main computer. I had to do it once because the shop forgot to do it.

Why do you need a whole single thing to do it?

Re:Solving my truck’s TPMS sensor problem with the help of a... by chiph on Monday August 22, 2022 @05:09PM (#32557307)
Some cars will auto-learn a new sensor just by driving a mile or so (the Hondas I have had). Others require programming. Why don't all car makers specify the auto-learning ones? No idea. Cost maybe.

The current SUV can be programmed to know 2 sets of five (for summer + winter sets), and you change between them via a switch under the steering wheel. It's common for new owners to get TPMS system errors because the switch got pushed by accident.

Re:Solving my truck’s TPMS sensor problem with the help of a... by KennyBlanken on Monday August 22, 2022 @08:21PM (#32559040)
> Why don't all car makers specify the auto-learning ones? No idea. Cost maybe.

Because auto-learning ones don't encourage a trip to the dealer, where the customer will go for new tires as well etc.

Re:Solving my truck’s TPMS sensor problem with the help of a... by loeg on Monday August 22, 2022 @05:27PM (#32557516)
Like the sibling commenter said, some cars just don't do it automatically (mine included).
Re:Solving my truck’s TPMS sensor problem with the help of a... by throwaway0a5e on Monday August 22, 2022 @06:25PM (#32558063)
There's no point in precise measurement because tire pressure is going to vary widely over temperature and how laden the vehicle is.
Re:Solving my truck’s TPMS sensor problem with the help of a... by KennyBlanken on Monday August 22, 2022 @08:25PM (#32559071)
Vehicle load changes the contact patch size, not the tire pressure (within reason.)

Over fifty degrees (F) you'll see 5psi change for a passenger car tire (30-40psi.) A 10 psi difference requires a 90 degree differential.

Re:Solving my truck’s TPMS sensor problem with the help of a... by horsawlarway on Monday August 22, 2022 @09:23PM (#32559457)
I've routinely seen estimates at 1-2 PSI per 10(f) degree change (depending on tire) and 50+(f) degrees of warming over the first 30 minutes of driving at highway speeds.

That's a change of between 12.5% and 33% depending on tire.

Additional load doesn't change the total volume much - so it's not directly increasing pressure - but it can increase deformation (as you pointed out - contact patch size changes) creating more warming, which will increase pressure.