3 ms·

The US spec requires detection of deflation independently, so indirect isn’t allowed as underinflating all 4 tires can’t be detected by indirect means.

• Amezarak 6y ago
  Honda cars sold in the US use an indirect system that works exactly as he described, so it must be allowed or Honda has gotten away for years flagrantly violating the law. NB: if you have one of these systems be on the lookout when you get your tires changed; a lot of chains will try to charge you for the tpms sensor when you don’t even have one.
  • corty 6y ago
    Some indirect systems use the first 10km driven after changing tires as a reference. Those systems can detect all four tires deflating at the same time, however, they need to be explicitly told via a special key combo or a diagnostic interface that you changed the tires just now. Maybe that is what they are trying to charge for.
    • Amezarak 6y ago
      Nope - they've never even seem to have been aware of that system, never activate it, and they charge per tire. At any rate, at least on the cars I've owned, it's been something along the lines "hold down this button on your dash for 30 seconds", so I'd be pretty irate about being charged for that even if they did it.