jmcraney

Sir, when the TPMS is in the Alarm State you can not adjust the warning thresholds by operating the Benchmark Set switch which is near the brake pedal root. You must get it out of the Alarm State to adjust the warning thresholds. One way to get it out of the Low Pressure Alarm warning state is to add pressure to the tire that is reporting low pressure, just as you did. Once you get it out of Alarm condition you may need to adjust it down sort of ratchet style - you might want to inflate it to 40 PSI and benchmark it (that would set the warning threshold to 30 PSI) and then set it to your desired benchmark pressure, say 33 PSI, (that would set the warning threshold to 24.75 PSI). Your difficulty was not the result of a defective wheel pressure sensor. You got out of it by adding pressure. The cause was a warning threshold that was too high or a tire that was under inflated.

If you benchmark all the tires at 33 PSI then the warning threshold for all tires would be 24.75 PSI. If you choose a different benchmark pressure for each tire, say 45, 40, 35, 30 and 25 then the respective warning thresholds would be set to 33.75, 30.00, 26.25, 22.50 and 18.75.

What you probably experienced was that your spare was benchmarked at 40 PSI. What probably happens is that the cars come from the factory with all tires benchmarked at 33. But the spare is inflated to 40 PSI to allow for permeation loss and seasonal temperature changes without accessing it which takes time. If someone operates the benchmark set switch while the spare is that high then is sets the warning threshold very high.

SW17LS

See, that's the informative and helpful post I have come to expect from you, not just a terse reply saying that we're all wrong.

That makes perfect sense, and it's entirely possible my spare had gotten down 1PSI or so lower than it had been previously and that tripped the benchmark. I didn't realize you couldn't set the benchmarks while the warning is on.

Rhambler

This just happened to me today. It's been cold here and my spare tire dropped to 29 PSI, which threw a warning!

My door jam says 33 PSI for all tires, spare included, which is what I set them to.

So, I filled it to 33 PSI, verified with my hand meter and drove off. Well, as soon as it registered the warning stayed at 33 PSI. Keep in mind, prior to today, it was at around 30 PSI with no warning, only crossing the 29 threshold did it throw that light.

So, remembering what Steve did, I filled it to 37 PSI and sure enough, it went away.

I'm going to deflate it back to 33 later, see what happens.

RayLS

I had 3 TPMS warning lights in the past 3 months so I took my car to the dealership last week at my SA's advice.
*Tire pressure checked manually when all 3 warning lights came on and they were ok - 40s (20 in wheels) and spare 33-35 psi (stock 17 in)*

SA said TMPS are good. Their techstream(?) could not pick up any error code(s) and the sensors were "communicating" with their reading machine.
NO new sensors. They even inflated all tires at 40 psi, including the spare tire

Well, it happened again this afternoon. This time I took photos and e-mailed them to my Lexus SA.
Measured the tire pressure - 44 psi x 4 wheels and spare reading @ 42.5 psi.
Called my SA and he told me to bring in my car (again). Told him I will IF they'll do something about the aging and mostly failing sensors (08 CPO LS).
He said will use the photos as proof of failing sensor(s).

jmcraney

Are you just sharing your experience with us, or are you seeking our help?

RayLS

@jm, just sharing.
Sorry for the confusion.

jmcraney

Thanks for sharing - we're always glad to hear from you.