Lifted from a previous post on here:
Reset of low tyre pressure
The threshold is set based on the tyre pressure which the reset function is executed by following procedure.
1. Operate the multi-information display switch to switch the information screen to the menu screen.
2. Lightly press the multi-information display switch to select “ ” (reset of low tyre pressure warning threshold).
3. Hold down the multi-information display switch for about 3 seconds or more, the buzzer sounds.
4. The warning lamp start flashing slowly.
5. Drive for a while. The reset is completed if the warning lamp goes out.
I presume (it's not clear from the text), that this will reset the threshold as a set amount below whatever the pressure in the tyres is when this reset procedure is done. If that makes any sense? So the sensors must be transmitting a value that the software interprets as a "starting point" for the warning function. You can't actually set a value of pressure, just a base point, from which the software calculates pressure drop. I've never fiddled with this, so I can't say whether this is actually how it works or not.
Regards, Ray. 2014 GX4H Glacier blue.
It's the 21st century - so where's my nuclear-powered flying car, then?