Tire pressure is the same rear: 40, front: 37; but tire light went on and the left rear reads 40 as does the right rear; but the light is yellow and says check tire pressure?

 

probably the spare tire in the trunk?

 

It could be due to the setting of the "reference" values. I seem to remember you can reset it in the tire service menu. I have seen the option a while back but probably will not be able to find it off the bat.
For example if it was set 39psi front and 44psi rear that your current values are too low.

 

Yes, just open up the Tyre pressure in your dash display and click the down arrow. Accept the new pressures and be on your way.
If you want to adjust pressures do it first then accept the new pressures and you are on your way.