Tire pressure

The tire-pressure light in a DANGER indicator, informing you a tire is 25% below the minimum. Waiting for that to come on is like using the smoke-detector as a timer for cooking.

Since tires naturally leak anyway, checing the PSI should be a routine part of upkeep. Every 1,000 miles is a good basis to start. But don't forget that cold temperatures outside also cause PSI to drop.

Lastly, measuring PSI can only be done when the air in the tire is cool. That means you cannot check immediately after driving. A $40 battery-operated pump is an easy way to add air at home, in the convenience & comfort of your own garage.
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Check the tp. Pump the tires to the desired pressure. Reset the monitor. Check regularly. If the tire keeps losing pressure then get it patched or replaced. No need to worry.

 

If a tire looks low, don't wait for it to cool. Check immediately for gross underinflation. Fine tuning can be done later when it cools.

If only one tire is low, you can check the others as warm tire reference points.

I have switched to a hand powered bicycle floor pump. It is faster and easier than re-stowing the power cord on my electric pump.

 

So I'm a bit unhappy with this whole TPMS system on the prius. The Pacific Industries TPMS sensors installed in the prius should supply pressure, temperature and acceleration data and the MEMS pressure sensor should be pretty accurate. Now, why can't I get the tire pressure readings in the car? I've seen other cars report the actual pressure. Is there a 3rd party way of doing this? Is it reported through the OBD port?

 

The scan gauge thread http://priuschat.com/forums/gen-iii...discussion/64406-scangaugeii-work-2010-a.html and Adrian Black's spread sheet list most of the stuff that has been located on the ODB https://spreadsheets.google.com/ccc?key=0AiHL0r_2nhUEdF9lVVBxOVNoN3Zva3E0NmdZTUR1eVE&hl=en
Tire pressure data is not there however. I think the Prius system just looks at pressure as a pass/fail parameter and doesn't know what the actual pressure is or which tire it's coming from. It knows that one of the four tires entered has pressure lower than the point where it was set to alarm. I think the alarm point is around 8 psi lower than the pressure in the tire when you initialize the TPMS.

 

Thanks for the threads! From what I understand, the TPMS transponders send the pressure, temperature, and acceleration data to the receiver. The Prius then compares the tire pressure data to the threshold you set. However the comparison is done digitally and thus the prius has the data. It is unfortunate that we can't find a way to read it out. The pacific industries website is useless, i.e. there are no data sheets. I looked around on the Japanese web site and it appears to have the same (limited) content.

Pacific Industrial Co., Ltd.

The wikipedia page is somewhat helpful:

[ame=http://en.wikipedia.org/wiki/Tire_pressure_monitoring_system]Tire-pressure monitoring system - Wikipedia, the free encyclopedia[/ame]

at least at explaining the different systems.

This site has a little bit of specific info although they really want to sell you a diagnostic tool:

Toyota TPMS - Toyota TPMS Tools & Tire Pressure Monitoring Systems

Still it is frustrating that the prius knows the readings from the pressure transducer but won't tell you. The little warning light is kind of brain-dead.

 

I didn't realize the sensors sent all the data, it is really to bad we don't have a way to access it. I had the pleasure of driving an '07 Corvette and was very pleased to see the pressures of all four tires displayed. The HUD was very nice also. If Toyota would include some of those things instead of the worthless IPA I would be happy to pay extra for them.

 

Best TPS system is a simple, straight forward manual tire gauge and checking the pressures at LEAST ONCE A MONTH. Every 1000 miles is another good pattern. Form a habit and keep it up. For those of us OLD ENOUGH to remember D) gas stations used to check your air pressure at EVERY fill up! (HA! How many of you are saying "Gee! I remember that!")

 

Gee! I remember that!

They also would check your oil & coolant levels, and clean the windshield. It was called full service. And gas was $0.50/gal. Now I feel old...

 

I took delivery of 2010 lll last week and checked my cold tire pressure the next day. Prior to me taking delivery, I asked the salesman if he would see to it that I had 40/38 in my tires. When I checked them I had 33/31...so the dealer never even checked the pressure. I put 40/38 in and tried to reset the TPMS but nothing happened. I am familair with the procedure since it is the same as my 2006 Matrix. (Turn ignition to on, hold in reset button until signal blinks 3 times, turn ignition off). I do not get the blinking tire sign at all. Could the dealer have missed initializing the system during setup or am I missing something?

 

I don't think you can assume that they didn't check the tire pressures. Since most cars are the factory with excess pressure to allow for time in transit, I would be willing to bet good money that they did check the tire pressures but over ruled your suggestion by going to the factory (or local dealer) suggested tire pressures.

Not that it makes it any better, but I seriously doubt that the car was the assembly point with 33/31 tire pressures.

That is actually much more annoying to me.

 

On the 2010 Prius, with car in ready mode, you hold the button until the light blinks 3 times and stops, and then you need to drive for a few minutes (according to the owners manual).

During PDI, the tire sensors need to be activated. Perhaps the dealer skipped this step.

 

Thanks for the response. If you look at page 443 of the owners manual, you will see that the procedure you just described is incorrect. It is as I stated in my post..Turn the “POWER†switch to ON mode.
Push and hold the tire pressure
warning reset switch until the tire
pressure warning light blinks
slowly 3 times Wait for a few minutes with the ON mode, and then turn
“POWER†switch OFF...which is what I'm doing and no tire pressure warning light blinks at all.

 

Hmmm, you own what is essentially a video game with wheels. It is loaded with technology and it is already equipped to continuously and remotely measure the tire pressure. Personally I want to see it. Then I can check the pressure daily and not monthly, with just a glance at the instrument console, and with a lot better accuracy, using a MEMS strain gauge, then the Bourdon gauge that has been baking in the glove compartment for years. It's a pity.

 

Well, these folks (and there appear to be many similar):

Toyota Enhanced OBD II

Claim they can display many tpms parameters through the OBD connector. This is under a section of their manual entitled "Live Data Sensors (non-CAN bus)". I know what CAN bus is, but some expert may need to chime in on what "non-CAN bus" means. Anyway this windows based OBD tool says they will read out the following for Totota/Lexus/Scion TPMS sensors:

ID1 Tire Inflation Pressure
ID2 Tire Inflation Pressure
ID3 Tire Inflation Pressure
ID4 Tire Inflation Pressure
ID1 Temperature In Tire
ID2 Temperature In Tire
ID3 Temperature In Tire
ID4 Temperature In Tire
ID1 Battery Voltage
ID2 Battery Voltage
ID3 Battery Voltage
ID4 Battery Voltage
ID1 Tire Inflation Pressure
ID2 Tire Inflation Pressure
ID3 Tire Inflation Pressure
ID4 Tire Inflation Pressure
ID5 Tire Inflation Pressure
ID1 Temperature In Tire
ID2 Temperature In Tire
ID3 Temperature In Tire
ID4 Temperature In Tire
ID5 Temperature In Tire
ID1 Initial Threshold Of Low Pressure
ID2 Initial Threshold Of Low Pressure
ID3 Initial Threshold Of Low Pressure
ID4 Initial Threshold Of Low Pressure
ID5 Initial Threshold Of Low Pressure
TPWS Trouble Codes

I would really like this on a compact tool like scangauge. I imagine one needs to find out the interrogation code to make an XGauge. I'm not that interested in installing a windows PC in the car.

 

Leaving aside the issue of what pressures anyone wants his/her tires set to -- factory, +2, +5, whatever -- it may be a good idea to "fool the TPMS system into giving you a meaningful warning.

I don't want a warning that I'm down 8 PSI or whatever on a tire. I want to know when it's down 2 or 3. (AND, by the way, yes, I do check tire pressure religiously. Every second weekend, both cars. Have a battery powered AirPro with which I can top them up with ease.) But that's all the more reason I want to know if I'm down a couple of PSI, because it can't be that slow of a loss.

I think when I settle on tire inflation rates (still running factory specs -- have only gone through two fill-ups since I took delivery, and I want a baseline), I'll pump the pressure several more than I intend to run, and then reset the system, then lower it to my intended level.

This way it seems as if I can get an earlier warning if a tire is slowly losing pressure. Sound as if it'll work?

 

You can do this by setting the TPMS when the pressure is approximately 8lbs above your desired alarm level, but there is a lot of hysteresis in the system. I doubt if you can get the light to respond to changes as small as 2 or 3 lbs. I was unsuccessful when I tried it, but it does work if you're down say 5-7 lbs below your set point. If you set it too close you may see the light when the car sits in the cold overnight and it will go out as you drive.

 

having a 2004 ... I just check weekly, and especially after the service center rotation. They always drop our pressues for 'comfort' rather than higher mpg's. Although these wireless aftermarket pressure do dads sure look tempting.



looks sweet ... don't know how accureate they are, or how often you have to keep up the batteries.
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