Calibrating TPMS for living at altitude

Hey everyone, I'm brand new to the TW community and looking forward to getting feedback on an issue that seems to get under my skin more than it should.

I picked up a '20 TRD Pro 6M last December and, in Golden, Colorado where I live (5,700' elevation), I've noticed the TPMS is off by ~3 PSI compared to the multiple gauges I own and trust to be accurate. There are other threads out there on this topic and I understand the explanation that physics provides for the discrepancy (absolute vs. relative air pressure). I've successfully gone through the initialization process to tell the ECU to see ~27 PSI as "normal" to avoid tripping the low-pressure warning when I drop 1 PSI — all seems to be good there.

I'm not sure whether the ECU or the sensors are responsible for assuming sea level when reading air pressure, but I'd really like to calibrate the system to take my home atmospheric pressure into account instead. Has anyone tried doing such a thing with success or failure? I've tried talking to my dealer about the issue but the shop rep's eyes glazed over as he went on about how expensive and accurate their tools are. I don't think he really understood the issue.

My old Wrangler JK read pressures that were almost spot on with my gauges at the same elevation so I'm guessing that system had a way to automatically or manually take atmospheric pressure into account.

Happy to be here!

 

Techstream would be the software that could possibly do this. Hopefully someone else can chime in that has used it.

 

I've noticed it being off slightly for me as well being at 4800ft. Honestly, you'll probably just have to end up knowing that there is a small difference between what the truck reads and what your gauges read. I haven't came across any threads during my time being on TW that discuss this, although that doesn't mean its not possible.

 

I've never lived at higher altitude, so don't know the answer, but I am curious.

 

I had this affect me on my summer road trip. We got up pretty high, and my tire pressures were all out of whack. I checked them with two hand held gauges and they were all even, and normal, but the TPSM system lost its mind until I got back down to normal elevations.

It’s not that they were so much wrong, but they were all displaying uneven, different pressures, which the tires in reality were not.

 

‘22 TRD Off Road 6MT lives at 8,000 ft. I have the same issue and have concluded (without verification) that the TPM system does not calibrate for altitude as most others do. So it assumes sea level all the time meaning that it will read low (incorrectly) at altitude. My dealer service department was comically clueless about how barometric pressure works as it relates to tire pressure and at a service visit for an oil change “corrected” my pressures to 36 psi based on the TPMS which means they were actually over 40psi. I gave up on trying to explain the science and now just know in my head that they read low and check periodically with a quality external gauge. Generally at 8,000 ft tire pressures will be 4psi higher that at sea level, meaning the TPM in the Taco will read 4psi lower than what the pressures actually are. I have found this to be correct through the external gauge. I set my pressures yesterday at 35psi all around and at the same ambient temp without driving anywhere the TPM shows 31psi. Attaching a chart from tire rack which shows the change in external air pressure at 1,000 ft increments.

 

It’s great that you want to make the sensors more accurate, however they are neither that accurate nor precise and you would also need another monitoring system so that you can reset each one for individual tire temperature variations as well. Interesting problem though!

Another project - turn your tires into altimeters!

 

I live at 3400 ft altitude. When I change tire pressure or make adjustments I just hit the tpms reset button and that works for me. I'm retired and have a lot of time on my hands but that is sure something that doesn't take up any of my time.

 

Actually they are quite accurate

 

Aren’t all of these reading gauge pressure? Are you saying the TPMS sensors are absolute? If so, they really went out of their way to build something that would be problematic.

 

Here's what I do

adjust tire pressure
reset monitor
drive

if a warning comes on because a tire is 10psi low all of a sudden
that means puncture

 

To read gauge pressure the TPMS sensors would require an external pressure sensor for barometric compensation. For maximum accuracy temperature compensation would also be required. These compensation addons would be prohibitively expensive and completely unnecessary for intended purpose of TPMS. As TacoTuesday1 says " If a warning comes on because a tire is 10psi low all of a sudden that means puncture" is all that's required from TPMS. Gas gauge is similar, it depends on a lever and float arrangement just like in a toilet flush box to measure tank level. No compensation for temperature, acceleration, deacceleration, tank angle, etc. It's cheap, simple, reliable and serves intended purpose.

 

That shows a level of precision, not accuracy.

 

Technically yes the TPMS sensors likely sense absolute pressure and that pressure is converted to gauge using a fixed constant (atmospheric at sea level). For the sensor to directly sense gauge pressure it would need to have some access to atmosphere which it doesn't being inside the wheel. It could use a reference sensor somewhere but now that's getting unnecessarily complicated considering the system's purpose.

 

i sorry, which one of those is certified to be accurate at the elevation it will be deployed at? do you have the compliance paperwork?

 

Not sure what you are going about.

 

this thread is about accuracy of the tpms at altitude. sure, you found a sensor and a pressure gauge that read similar, but how do you know they're not just inaccurate by a similar deviation?

 

I live at 1000ft and all my gauges show 2psi more than the stupid factory tpms.

I hate it, because I have to get 2-4 psi higher due to temp changes, then another 2psi because of the damn tpms reading wrong.

 

I have 3 cars, total 12 sensors, same bike pump, same pressure stick, plus obd2 app to see tpms control unit (pressure, temp,etc).
Good enough?
I'm confident.
P.S. here is for the science. 2 different sticks measured at LF tire (ID2)

 

FWIW not sure if this is after driving
But driving changes it. Cold psi is cold, then a mile of driving or more becomes hot PSI aka +4psi.

ie truck is driven to Costco self serve inflator
Cold spec 29
Air to 33. It should drop them all to 29 cold at night per door sticker.