had snow tires mounted inflation light?

If you originally had your TPMS set for 40 psi and they filled your replacement tires to more than 30 psi, then there would be NO alarm. (Assuming the TPMS sensors stayed on the tires.)

To check the system:

1) Measure your present tire pressure,
2) Reset your TPMS system,
3) Lower your pressure by at least 25 % (original: 40, lower it to less than 30 psi -- 1/4 of 40).
4) Check your system. You may need to drive a little before the light comes on.
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Be SURE to REFILL your tires after you're through.

This works in my TCH, but YPMV (Your Prius May Vary), however, in this case, I doubt it.

 

I too, just bought a set or snow tires on rism all mounted, do not know if there is a TPMS sensor insdie or not.....will this harm anything? Other than Toyota, where can I buy the sensors?