From the online manual.  No 5.  This confirms my original post.

If I recall correctly I think the manual says it's a temperature sensor.

If they are run flat tyres remember they are designed to run with no air at all in emergency and they do not need high pressures to keep the side walls from collapsing.  I have always run mine at the pressures on the door pillars and have never had any issues with control or with uneven wear.