NX300 2018, 7 months old.
In this very cold weekend (13 F on Friday), the warning light came on and the readings are 30 PSI on the small screen.
Today (51 F, on Monday), they are back to 34 PSI as before the cold days and warning light goes off.
Is this normal? or something wrong? or sensors' issue?
Tire pressure changes too much between cold days and warm days.
However, this summer it didn't change that much, just going up from 34 PSI to 35 PSI even in very hot days.

 

The TPMS warning light comes on when the tire pressures are a few pounds lower than they were the last time that the system was re-set.

I don't have an NX. So, I don't know where the re-set button is on the NX, but, on other Lexus models, it is either below the left side of the dash or in the glove box. I'm sure that your manual will say where it is on the NX.

If you re-set the system with that button, the warning light will not be triggered unless the tire pressures fall several pounds below their level at the time when the re-set was done.

However, if your system is reading pressures of 30 pounds on those cold days, that is an indication that, for the winter, you should be adding a few pounds of pressure to each tire. After adding more air, you should, at that time, re-set the system as I described above.

 

Based on tire temperature the air pressure will vary usually by 3-4 PSI.

1. Park the vehicle in a safe place and turn the engine switch off.
Initialization cannot be performed while the vehicle is moving.
2. Adjust the tire inflation pressure to the specified cold tire inflation pressure
level. Make sure to adjust the tire pressure to the specified cold tire inflation pressure level. The tire pressure warning system will operate based on this pressure level.
3. Turn the engine switch to IGNITION ON mode.
Press the pages button on the right side of the steering wheel then press the right or left arrows on the steering wheel until you get to the settings icon (Gear) on the dash.
4. Then press the select button (dot button) on the steering wheel.
5. Once selected use the up or down arrows on the steering wheel until you get to TPMS then press and hold select (dot button).
6. You will see a message displayed indicating that the TPMS has been reset.

This will become the default tire pressure. Note that you must do the above with the tires cold.

Hope this helps.

 

Thank you - lesz and MKenM, OK, It seems normal, then it's good for me. I had a Prius 2008 before, the tire pressure didn't change this much between cold days and hot days. Probably the small size of tires explains that. Larger tires may have more space for air to shrink when cold. Thanks so much.

 

Typically, regardless of whether the tires are larger or small, the change in tire pressure will be about 1 psi for every 10 degrees in temperature change. So, if typical daytime temperatures drop from, say, 70 degrees to 20 degrees, it would be likely that tire pressure would drop by about 5 pounds.

Also, while driving, the temperature of the tires and the air in them can rise by 30-40 degrees or more. That means that the tire pressure can rise by 3 or 4 or more psi once the tires are warmed up by driving. That is why pressures should be checked and tires should be filled to the proper pressures only when the car has not been driven for at least a couple of hours and the tires are still cold.

 

Thanks for the info. Will reset the TPMS once tires are filled to appropriate pressures.