TPMS Sensor Intermittent Error

Our 2013 has been virtually trouble-free over the 33K miles we've driven so far. Our 2008, at 90K miles, has also been absolutely bullet proof. Both vehicles are a testament to excellent engineering and quality control at Toyota. Interestingly, the only recurring issue on our 2013 has been with the TPMS which throws a TPMS warning light whenever we go on long trips (for instance, from Los Angeles to Northern CA). The problem has never occurred during shorter trips less than a couple hours and does not occur during my regular commute.

First off, I check cold tire pressures at least every two weeks and I run our 2013 at 38 front/36 rear. The first time the TPMS warning went off we were about three hours into a nine hour trip. I pulled over and checked the tire pressures - all were fine. Outside temperatures were about 85F. The warning came on several times (first flashing, then solid) several times during the trip but subsequent checks showed all the tires were just fine and within 2psi of each other. When I returned home, I took the car to the Toyota dealer where they ran a TPMS scan and found no problem (of course, no TPMS warning at this time). They "re-calibrated" the sensors and sent me on my way.

Since then, the TPMS warning has occurred again during several long trips. It has not occurred when traveling in ambient temperatures of 70F or lower. Returning to the dealer never reveals a TPMS error on their scan tool. I'm fairly certain one of the TPMS wheel sensors has an internal fault that is aggravated when the wheel/tire temperature is elevated in 85F or higher outside temperatures. Unfortunately, the sensor returns to normal operation at lower temperatures and works normally most of the time. But the warning light is a nuisance on long trips in hot weather. If the sensor finally fails outside of warranty, I'm hoping that Toyota will look at our service records and note that I've been in twice for the problem.

Anyone else experience intermittent TPMS sensor problems?