TPWS warning light turned on this morning

So naturally I thought a nail had punctured a tire leading to a slow leak. When I got home I found no nail and the tire pressure on all four tires even but down to about 36psi.

I refilled to my normal of 40/38 and reset the TPWS system with the button below the steering wheel. The light stayed on for a minute or two of driving then turned off and stayed off for my commute to work.

What I think probably happened is that I reduced from 42/40 to 40/38 recently without a TPWS reset. Then this morning the temperature outside was 55F and about 65F in my garage. When I left the garage at 5:20AM the TPWS light was off. I drive about 2 mile to the gym each morning and park my C for about an hour. This morning, when I got back in the car the tires had cooled to 55F and I guess that was enough to reduce the pressure far enough to trip my warning light.

Iirc the manual says a 4-6 psi pressure change will trip the warning light.

Anyone else had false alarms like this now that the weather is getting cooler?

 

I found an interesting article on the Toyota TPWS.

http://www.toyotapartsandservice.com/pub/pdf/TechCenterLibrary/ToyotaStarServiceNews/2005/Fall/Toyota-Pressure-Warning-System.pdf