Metal valve stem caps. Ugh...

Yeah, plastic is better. That sucks.

 

Did your car come with metal caps? Mine were plastic. I notice one is different, though. The dealer had checked that tire for a leak and must have put a different plastic cap on the stem.
If yours had OEM metal caps, I agree it would be Toyota's issue and the stem should be replace under warranty.

If you placed the metal caps on yourself, that is different. I have not seen metal caps used on a car in years.

 

What do you expect Toyota to do? You replaced a good, tested part with something inferior.

 

It may look better on chrome wheels, but aluminium stems also corrode. If I ever have to replace TPMS/valve stem on my car again, I am going with after market rubber stem TPMS like this one.
Schrader EZ-sensor
Many of aftermarket TPMS are two pieces design, and if stem piece need to be replaced, it cost only a few backs.

 

My local dealer does not know how to properly service the Prius. On my 5K check, they said they set the tire pressure to 32 on all wheels. In actual fact, i was a more reasonable 39.
I did my 10K oil change myself to be sure it was done correctly.

 

Late now, but holding the barrel of the valve with needle nose pliers (the kind with a 45 degree bend at the tips) while trying to loosen the cap might help.

 

Ouch!
I had a similar problem with one of mine, but was able to repair it and my local tire guy warned about using metal caps, so now I coated the threads with a tiny spot of grease to help stop the seizing! I have my winter wheels on at the moment, they don't have TPMS, but I use these instead:

 

I'd try dribbling a drip of WD-40 or similar down the valve stem (park it so it's upside down) and leave it for an hour or 2 - hopefully it'll penetrate it. Failing that, tap the cap gently with a small peen hammer on one side with a panel dolly held firmly on the other side - that should break the rust bond.

My last car had plain metal caps and I never had a problem. I use them on my bicycle as they seal better as they have a neoprene washer, and will hold air in even if the valve leaks (the plastic ones don't hold air). Not sure why valves leak more often on bicycles than cars?

 

TPMS sensors/valves should be less than half that. Try a regular tire shop next time.

 

I put 80-120psi in the tyres on my road bikes and 60-80 (or even less) in those on the mountain bikes. (...just a thought...)
PS: I changed all my bike tubes from Schraders to Prestas as Prestas have positive seals rather than tiny springs!

 

I think my (road) tyres say on the side-wall 55psi which is what I pump them to. And the tyres are getting old so I don't take them past that any more. Rough as anything for the first week after pumping up.

I've had a sore shoulder the past few months (hurts going up hills, but fine going down again), so haven't been riding, so they're probably close to flat now.

 

Didn't you needlessly pay $200 for a replacement TPMS sensor, at a Toyota Stealership?

While this one was prematurely and needlessly put out of service, those sensors don't last the life of the car. They will need replacements sometime, such as when the internal battery reaches the end of its life.

So when sensor replacement is needed again, find a more normally priced tire shop instead of a high-markup car dealership.

 

The TPMS is a $50 part.

Your 'expensive mistake' was letting the dealer near your car.....