If the light comes on and your four tires are good, check the spare. Mine was at 40, it should have been 60. Yeah, you may have to dig thru all your junk in the back and the spare is mounted upside down, but check it. This was after the warning light came on, I checked all four and they were good.

http://owners.honda.com/vehicl...re-Monitoring-System

Mine is a 2017 and the manual doesn't say, but I think there is a sensor/transmitter inside the donut spare. Can anyone confirm this?

I have never seen a TPMS in a donut spare. Some full-sized ones do have them. Are you saying you had the light on and it went out only after you aired up the spare? On a '16 model I worked on the other day, the TPMS was indirect and there was a reset button on the lower left side of the dash, totally unlike most other late model systems.

Your spare being one-third under-inflated wasn't a waste of time.

quote:

Originally posted by egregore:

... Are you saying you had the light on and it went out only after you aired up the spare?...

Nope. The light came on, I checked all four (they were good) and I grumbled and reset the system. No more warning lights. A week later I decided to check the spare and it was low.

Well, if the light is out and hasn't come back on, take yes for an answer.

Indirect TPMS uses the wheel speed sensors as the input, not actual pressure sensors. I presume a low tire would turn slower than the other wheels. On direct measurement systems, the threshold is usually around 5-6 psi low.

quote:

Originally posted by egregore:
a low tire would turn slower than the other wheels.

Interesting. That's counter-intuitive. I would think that a wheel with an under inflated tire would have a shorter working radius (or diameter), and that wheel would have to turn faster, not slower, than the others.

Your spare does not have a sensor. Your tires do not have sensors any longer either. Honda has gone back to passive TPMS being monitored via ABS wheel speed sensors.

quote:

Originally posted by F12517:
Your spare does not have a sensor. Your tires do not have sensors any longer either. Honda has gone back to passive TPMS being monitored via ABS wheel speed sensors.

So why did the warning light come on if the four tires were good but the spare was low? It was not the first cold day of the season.

FWIW, the light came on a couple months ago, but the right front tire WAS low. I filled it, but a few weeks later the dealer could not find anything wrong with the tire.

Forgot to add I have the cheap system that does not specify which tire is low.

Good thing sdince their wheel based sensors were so fragile.

RMD

I had asked 2 different Toyota dealerships and 3 other mechanics/tire shops about my TPMS light (I asked as a side-note; it wasn't what I had them working on) and none of them thought to tell me to check the spare on my wife's Rav4. It wasn't until I mentioned it to the Costco Tire guy as he was looking up some tire prices and he said "probably your full-size spare" like he'd had that issue before. sure enough. fucking full size spare must have a TPMS thing in it, because it was at about 20psi. filled her up with air and the light went off.