orrmin

Turns out to be an incredible coincidence. The master/secondary pushbutton under the glove compartment was accidentally pushed in by someone or something to the wrong position. The manual says the system takes about an hour to notice this, and indeed it was about an hour into the trip when the light began flashing (although being alongside the duplicate Lexus may have somehow goosed things). A suggestion to Lexus: put a cover over the pushbutton. This feature is much more likely to be accidentally triggered before having to actually be used by a customer.

Driving 2007 ES350 at the freeway limit (70mph), all tires including spare at recommended 30psi. TPMS light starts flashing, then stays steady (supposedly indicating problem is with monitoring system, not tire pressure, according to owner's manual). Reset button has no effect. Haven't yet made it to a dealer for diagnosis, but... ...the warning light happened to first come on AT THE EXACT MOMENT I WAS ALONGSIDE AND JUST NOSED AHEAD OF WHAT APPEARED TO BE AN IDENTICAL (2007?) ES350! Even the color was the same. ES350 TPMS uses unencrypted radio frequency transmission, does it not? Even though unique (car? wheel?) identifiers are supposedly used, I'm predicting that Lexus firmware has a bug such that competing (dopplered?) RF signals can force a TPMS failure mode!