Tire pressure gauge not working with spare tire

Yes same valve you should be getting a reading can you touch the center pin and the Schrader valve with the screwdriver and hear air coming out?

 

You might have to take the spare out and flip it over for access to the valve.

 

Yes, it does. I read my spare's pressure with the same gauge as the regular tires, and can see no reason why your pictured gauge might not. It has the right head, and a sufficient pressure range.

Are you not finding the spare's valve (stored normally in the trunk, it is on the bottom side), or are you getting no reading (e.g. flat, no pressure remaining)? Or are you not getting the head onto the valve straight?

 

maybe the pressure is too low to get a reading. can you set your compressor?

 

maybe the end of the schrader valve is damaged

 

What kind of gauge? Has it got sufficient range; spare is 60 psi.

If this is first time you checked it, it's guaranteed to be low?

When we purchased our 2010, paid full Pre-Delivery Inspection, spare tire was at 40 psi. 12 volt battery was dead as a doornail too *. They tried to hide that...

That was at Open Road Toyota in Port Moody, the "not so good" guys.

Oh, and they said documentation was "included", on the first paperwork. Rewrote it, and "included" morphed into $295 CDN. Were actually miffed when I called them on it.

Charged $400 CDN for installed block heater.

And when I asked about Toyota steelies for snow tires, said there were none, since the Prius was a "flagship vehicle". Westminster Toyota helped me out there.

Lessee, what other dirt have I got. Better shut up... They might sue...

* We bought our cream puff in November 2010. It was dust covered, way back of the show shed. See later, the build date was August 2009. Still it's been champion.

 

Maybe finicky connection. I'm using a few pen-style, and a very cheap digital, all work ok.

 

the pin might be good, but maybe the threads are bunged

 

What's the minimum pressure your gauge will show? My guess is that the pressure is below that, but not low enough to subjectively seem flat

 

Tire gauges just aren't anywhere near complicated enough to be playing "oh, this is the spare tire, I'll do something else just to be ornery" games.

 

Sometimes I find a similar issue. My issue is that between measuring the pressure measured changes, or the (digital is what I use) gauge may not read anything.

I suspect the valve has been installed into the stem too tightly, or it’s somehow different dimension the pin is too deep for the gauge to press it. The best solution I can think of is to have the complete valve stem replaced, or at least remove the valve and re-torque it, replace with a new one….

EDIT:
I have one of these but point is there’s a torque spec for the valves and I’m not sure they are all torqued to spec:

https://slime.com/products/pro-series-valve-core-tool

 

I remember the valve stem on the spare had to be moved a tiny bit to get a good reading when checking the pressure because it was really close to the rim. This was when I had both my 2010 and 2017 Prii.