Works for me!

 

The sad thing is, Chevy could make them read correctly at all altitudes. Our cars have a barometric pressure gauge, the BCM COULD use that to reference the TPMS readings.

 

That isn't accuracy. That is resolution. Accuracy is the same whether or not the display is shown in metric or english.

The same can be said about the other gauges as well. Pencil gauges are about the same accuracy as the most expensive gauges they just have a lot less resolution. No matter which gauge you are using you only know if it is accurate by having it calibrated against a known standard. Without that it isn't any better or worse than any other gauge other than for resolution. Given the number and types of gauges on the market it is interesting that most come within a pound or two of the average of all of them.

Bill

 

especially with the wheels parked facing the sun.

 

Yes, True but at least all tires would be within 1/10 of a KPA of eachother. I suppose the question is what other tire pressure guage is accurate to what degree and how much that would matter ( when relating to altitude )

 

I remember years back that one supplier company had a filler set up consisting of 4 wheel devices and a intake on hoses long enough to hit all 4 wheels at once. Now that's dedication!

 

Mine are a couple psi off at VIR and I don't think VIR is at any significant altitude. I didn't realize this until I got a reality high quality analog guide that lets you equalize the pressure in the gauge before you read the tire.

 

With the sensors being inside the tires, they can only read the absolute pressure, whereas a tire gauge is giving you the relative pressure. The car's ECU does the calculation to convert the absolute reading of the sensor to a relative reading.

If your car was delivered at or near sea level, and then you move to a higher elevation, the dealer can do an ECU reset to recalibrate to the "home" altitude and then your DIC readings will be accurate again.

 

In my previous C6 that had a different system than the C7 for linking the tire pressure monitor to the cars readout, the instrument I used could be used to get a static tire pressure reading. It read to a tenth of lb, as in 30.5 psi.

 

With Bill's post above in mind, I cannot tell you precisely how accurate my Vette's TPMS is. However I can say that the TPMS results have matched my hand-held every time measured. (roughly a dozen times since car acquired in August, 2016.)

 

My plastic digital gauge matches my TPMS to the pound, but I don't know if the gauge is any good, and I live at 50' above MSL.

since the car was built in KY, wouldn't the TPMS be calibrated for the elevation in Bowling Green, about 550'?

 

TPMS sensors measure absolute pressure. It's not like the pressure changes inside when you get to higher elevation (assuming temps stay same), but the pressure delta relative to ambient pressure will change since now there's less air (pressure) outside.

As others stated, you can measure with an accurate gauge, compare against what TPMS reads, and come up with the offset value to interpret what you read on the dash.

Accuracy is usually either +-1 PSI, or +-0.5 PSI as far as I see on sensor manufacturer sites. Since accuracy is already not too high, higher resolution reading might not help much, besides making you paranoid : )

 

Hmmm.....thanks for the info - I had no idea that they could/would do that!!

Butt...living on the east coast at sea level I don't have any discrepancy between my DIC readout and my gauge.

It's kinda curious why with the supercharged C6 ZR1 and C7 Z06 that every time you start the car, the ECU resets the boost gauge so that the "zero" indication on the gauge is exactly ambient barometric pressure.

Why that feature isn't tied into the tire pressure sensor readouts, I dunno!?!?

.

 

Below are several pictures of a couple different TPMS tools. They may indicate pressure to 1/10th or even 1/00th of a psi, but if the tire pressure sensor is only accurate to 0.5psi, then the higher gauge readout resolution doesn't mean much.

In the 3 C6 Vettes that I owned, and now the C7 that I have, I have had a couple sets of wheels/tires for either the street or track, and of course with the C6 you needed a TPMS tool to relearn the sensors into the TPMS computer module in the car each time you swapped on a new set of wheels with different sensors. It's great that the C7 now "auto-learns" a new set of sensors!!

I've had a bunch of different sensors, and I ALWAYS use the OE Schrader tire pressure sensors!! I've never had any problems with them, and I've read quite a number of posts where owners using aftermarket sensors have had problems.

Below is a picture of a Cub Pro-101 TPMS tool reading the pressure in a 2009 C6 ZR1. You can see it's reading out to 1/100th of a psi, but if the sensor is only accurate to 0.5psi, then that real accurate looking readout may not be quite that accurate!!




With the 2010 model year, the TPMS computer module in the car was changed and required a different sensor - one that had been used in the HHR and other GM vehicles for several years, and in addition to pressure it transmitted temperature to the TPMS. You can see below that the screen says "HHR" at the top - that's because that tool only had up through the 2009 model year vehicles. To read sensors in a 2010 or newer C6 I had to select a car that had used the same sensors, and the HHR had them in 2009 and a couple years earlier. You see it's the same tool as above, but is only reading out to 1/10psi, but it also is displaying the temperature - which in this case was the same as the ambient temp of 78°:




Below is a different tool that reads out to 1/10psi. This was a readout from a 2010 C6 that had just come off the track at Sebring. I believe he started out with a cold pressure of 28psi, and you can see that the pressure went up to 36psi with the temperature increase from aggressive cornering on the track:




So....:

• I believe our OE sensors are probably quite accurate to about 1/2psi.
  
  
• As was indicated in a previous post, you can't set pressure with the readout in the DIC - the TPMS just doesn't update fast enough to be able to do that.
  
  
• Get an accurate gauge (and most are probably +/-0.5psi) and use it to set pressure of all your tires regularly when the tires are cold.
  
  
• Our TPMS just does not adjust the DIC readout for the ambient barometric pressure. As you drive to higher elevations the DIC display will be somewhere around 3/4psi lower for every 1000ft higher you go. In mile-high Denver the DIC will show around 4psi less than when you check pressure with your gauge.

.

 

I don't believe this is true. It was not true on the C6 Vette, I asked the Bowling Green engineers, they said the TPMS would read low at altitude. I will try and research this with a knowledgeable GM Corvette tech and get back to this post with the answer.

 

with 6Speeder. I'm skeptical that the ECU can be reset to any other altitude. Butt....I'll standby for documentation that it can be done!

As I mentioned, in the supercharged C6 and C7, the boost gauge is automatically zeroed to local ambient barometric pressure every time the car is started, so if you mess with that function for one system, you might screw it up for other systems.

Why the TPMS isn't kinda hooked into the altitude correction that's going on for boost to display properly, I dunno!?!?

.

 

My two handheld gauges read identical pressures but the TPMS always reads 1 to 2 psi lower on my 2014 C7

 

Well....where you are located is not in your avatar info, so I looked in your profile - but nothing there either.

If you live somewhere at about 2500' elevation, then as we've been saying, that's exactly what you should expect.

Another thing that you need to do before comparing the pressures displayed by the DIC and your gauge is to drive around for a few minutes at greater than 20mph. That will wake up the tire pressure sensors and get them to transmit the CURRENT pressure to the TPMS so that is what is displayed in the DIC.

When the car sits still for more than about 15 minutes the sensors go into a sleep mode to save their internal batteries. If the car has been sitting for, say, overnight and you check the tire pressures with your gauge, then start the car and before driving look at the pressures displayed in the DIC, you may have a couple psi difference. Drive the car above 20mph for a couple minutes to wake up the tire pressure sensors and get them to transmit the current pressures.

So....you should air up your tires to the recommended psi with your gauge when the tires are cold, but don't compare the DIC pressures until you've driven for a few minutes so the sensors will wake up and transmit the current pressures to the TPMS.

.

 

Same here

 

I can second this. I am in Denver (5200-5300ft) and the TPS sensors are consistently 3-4psi lower than a quality gauge read.