Checking tire pressure?

I set the TPMS alert threshold much higher than normal. The way it's set (in my generation, gen 3, anyway) is by pushing a button under the dash, and then it looks at whatever pressures the tires have now, and sets the alert threshold for a substantial percentage below that. Like, if I pushed the button when my tires at at their normal pressures, I would never get alerts unless they dropped into the mid-20s psi.

So instead, I pumped my tires up just once to the max sidewall pressures, and I pushed the button then, and after that I let them back down to the pressures I normally run.

That means I get the yellow TPMS light when they're just a few psi below my preferred pressures, and I air them up right then.

It can be a bit of a nuisance in the spring and fall when temperatures change a lot, because every sharp temperature drop lowers the pressure enough to put the light on again. But then, I wanted to know about that, so I guess that's what I signed up for.

 

My Gen 2 doesn't have that. All I have is an unadjustable alert that a tire pressure is low and located on the far right of the display, near the passenger so it's easy to miss, plus the sound alert isn't strong as well.

To make it worse, when switching wheel (like from summer to winter), you need a software to swap the TPMS IDs stored in memory. It's either Techstream through a mech/dealer ($$$) shop or the Carista app with a monthly subscription ($). I subscribe twice a year, April and November.

But to answer the question, I check the pressure when I change the wheels and when the TPMS says one is low.

 

Every fill-up.

 

Your gen 2 doesn't? That's odd. This drawing from a US 2008 owners' manual shows both the light and the button, described pretty much the same as in my gen 3.



I think some of the earlier gen 2 years in the US didn't have TPMS at all: no light, no button.

I hadn't heard of any with light but no button. Maybe Canada was different?

 

For those of us who don't game the TPMS thresholds the way Chap does, waiting for the TPMS warning light really means letting the tire get too low. I didn't want to run on a near-threshold tire for an extended period, so checked my Priii with a gauge more frequently.

Now that I have a newer RAV4 Prime, all that is fixed, as one of the rotating selectable displays shows the pressure of each tire. One can see the tires warm up on the road, and even distinguish between the sunny and shady sides of the car.

 

Me? Every quarter.
Monthly? Very good maintenance habit

'17 V only has TPMS low pressure, not a readout of actual pressures.
Yes TMPS readout could make me lazier

 

I meant its TPMS isn't adjustable. It's fixed at 26 psi. Which is the usual value for standard 32 psi tire but the Prius is 35/36 psi.

 

Actually the low tire pressure alarm point by law is 75% of the tire pressure at the time the "set" switch is pressed. If the tire pressure is 35 psi the "set" low alarm will be 26.25 psi. Each tire will have its own alarm point and all four alarm pressures remain in the tpms ecu until another "set" procedure is done.


This screen shot from a recent gen2 Prius tpms sensor change was taken after the new id codes were written but before they were installed. Once written the vehicle's tpms ecu picked them up showing their current pressures, temperatures and sensor battery status. This proved each sensor was good prior to installation.

The previous "Initial Threshold of Low Pressure" alarm points remained the same and were based on a nominal 35 psi in each tire. After sensor installation the tpms system worked with no warnings or codes.

If I had set all tires to 40 psi and did the tpms "set" button alarm point initiation, the revised alarm thresholds would read 30 psi. If I then adjusted the tires back to 35 psi the alarm points would remain at 30 psi providing a much quicker tpms pressure warning. So the alarm points are adjustable but not through Techstream.

There is a method to clone one set of tpms sensor ids to a second set of sensors for your winter wheels and tires. At that point no seasonal tpms id changes are necessary.

It does require a set of Autel MX sensors and an Autel tool to write your first set of ids into the MX sensors. A set of four MX sensors are currently $109 on Amazon.



Most of the better tire shops already have the Autel cloning tool including Costco. Or you could buy an Autel TS408S or TS508wf. This tool also directly reads sensors (id and data) already installed and can read and write a Toyota tpms ecu. No scanner required and works on almost all vehicles.

 

I see rj has covered this also, but just for the short version, the presence of the button (as seen in the owners' manual drawing I posted) means that it is adjustable. The button is how you adjust it.

 

TPMS initialization (low pressure alarm set) from gen2 owners manual.