Does tire pressure monitor indicate "too high" pressure?

No, it only indicates on low pressure to alert to a possible flat tire or a tire with too little pressure. The Owner's Manual makes no mention of high pressure.

 

How much pressure did it have?

Blowouts from overheating from too little pressure far outnumber those from too much pressure.

 

Your right about Prius being packed with technology but falling short on seemingly simple upgrades. There are lots of threads about options/things missing from Prius that should have been on the car. I suppose, however, if Toyota added all the little things, our Prius would cost twice what we paid!

 

I agree that price could be for most people a major concern, adding wt. to the car is a concern, but adding things like voltage readings on both batteries, being able to set the seat belt and back up beeping, actual tire pressure, engine running light would be nice, wouldn't cost all that much to do???

 

I would also estimate that it has a lot to do with making the car simple. If you make a car that has a million readouts on it, many people will be turned off by that - "it has all these things, I don't know what they do or mean, I can't possibly be smart enough to drive this car." I'd say that's doubly true for things that don't exist on non-hybrids, as they want the car to appear as much like any other as possible, and keep the hybridness out of the way of the driver.

It can also be a question of engineering resources (more gauges means they need more engineers to design them, and more testing to make sure they work right), increased failures (more things that can break), and return on investment (if I spend $x to add a battery gauge, will that cause many people to choose this car over another model such that I make at least $x of profit? And an even harder challenge to meet for these gauges - can I spend the same $x to add a different feature that would do even better?).

 

How about including it on the cars with Nav and have a programmer stay late one night and make it a page or screen?

 

Trust me, you do NOT want an engineer designing a user interface.

(And yes, I am an engineer.)

So you have to have one person write the code to display the data, another design the user interface, an artist might be needed for any graphics, somebody else to test it and make sure it works right (plus test it in various conditions - what happens if the sensor is at its maximum or minimum? Or if it's giving a value that's clearly an error? Or doesn't respond?)... And that's completely ignoring all the planning; writing a specification for how it should work, for example (plus the requisite arguing over how it should work, as well as reviewing the spec). And since the Nav unit is from Denso, but the car and sensors are provided by Toyota, you probably have to cross a few layers of management and bureaucracy as well. Even something seemingly simple like this is quite difficult when you get to be the size and importance of Toyota.

Now if Bob the Builder down the street makes custom cars in his spare time, I'm sure he'd be happy to spend an afternoon coding something like that. Unfortunately for you, cars aren't typically something that any random person will build (nor would most people buy a car for which there's no guarantee of future parts or serviceability). So, we're stuck with the Scangauge and similar devices, which can read out such sensors where they are available.

 

I don't know the answer to the question but there was http://priuschat.com/forums/prius-hybrid-news/83166-prius-tire-explosion.html on a 2nd gen.

Side note: On the 03 Nissan 350Z w/sufficient equipment level, their TPMS would also show the tire pressures on the display of all 4 tires. I believe you had to be at least one trim level above Enthusiast (mine, which has no TPMS), so that would've included the Performance and the 2 trims above it.

How do I know this? My former coworker had an 03 350Z w/the above TPMS and I'm 99% sure it was Performance trim. He complained about all sorts of problems w/the TPMS being off. IIRC, it'd complain his tires were low, when they weren't, so he had to overinflate. I know he complained about it but I don't think he ever was able to get a dealer to fix it.

I believe on later years of Zs, Nissan ditched display of tire pressures completely. I don't know the reasons why. I can only speculate.

FWIW, my mom's 07 Altima Hybrid will NOT show tire pressures. It has a dot matrix display that can display anything it wants to, but no tire pressures are there. When the tires are low, the yellow ! w/tire icon light comes on. I've seen it come on at least 2x myself on her NAH.

 

That's another good reason to not show the pressures to the driver; often these sensors are extremely inaccurate and uncalibrated, in order to save money. All the sensors need to do is sense a 25% drop in pressure from some set point. That's pretty easy; it's not too much more difficult to make some number that's roughly proportional to PSI. But then getting that number to be close enough for user use (probably ±1 PSI at worst, ±0.3 PSI or less would be a better design) can be difficult.

For TPMS, each sensor is calibrated to itself when you press the reset button, so any inaccuracy in the sensor is accounted for. It knows when it has dropped 25%. What it doesn't know is the real pressure in the tire when it's calibrated.

I've seen temperature sensors in semiconductors that have accuracy of ±12°C. If you used one of those in a thermostat, you might set the heat to 20°C (68°F), and the actual temperature would be somewhere between 8°C and 32°C (46°F to 90°F). That sensor was designed to measure approximate temperatures, as well as (probably more accurately) change in temperature over time. Similarly, tire pressure sensors are probably equally unreliable when compared to an absolute measurement, though satisfactory for relative measurements.