So my front left Tire pressure monitor is either bad or going bad. It will randomly stop working for no reason. I'll be driving down the road and it will flash "service tire monitor". sometimes the pressure is off. it was flashing saying my tire pressure was low so I went to fill up the tire and I used my manual gauge, which showed 31psi. The sensor said 26.

How do you replace it? I thought about buying one and doing it myself but im not sure where it is.

 

its located on the rim. when i had my tires changed they charged me 20$ to put new sensors on all 4 rims at discount tire.