Grenadier TPMS vs ARB Gauge Readings

[Notmycamel]

Hey everyone, looking for some input on a tire pressure discrepancy on my Grenadier.

Vehicle has Toyo Open Country RT Trail 35x12.50R17 tires and I’m running Apex Rapid Deflator valves on all four tires.

Using my ARB digital inflator/gauge directly at the valves, I got these cold-ish readings:

Front Left: 34.5 psi
Rear Left: 37 psi
Front Right: 35 psi
Rear Right: 35.5 psi

But the factory TPMS screen in the Grenadier shows:

Front Left: 39 psi
Front Right: 39 psi
Rear Left: 38 psi
Rear Right: 39 psi

So the TPMS is reading roughly 2 to 4.5 psi higher than my ARB gauge.

Questions:

1. Has anyone seen the Grenadier TPMS consistently read higher than a trusted handheld gauge?
2. Could the Apex Rapid Deflator valves affect TPMS sensor accuracy or sealing in any way?
3. Is the likely culprit the ARB gauge calibration, the vehicle TPMS calibration, or the valve setup?
4. Which reading would you trust more for daily use?

For context, tire temps on the screen were around 81 to 90°F when checked.

Appreciate any real-world experience before I start chasing ghosts. Any advice how to calibrate the TPMS for accuracy?

 

[C-Mack]

I’ve noticed the same with mine the TPMS screen is off about about 2 psi. Verified my pressure gauge is accurate against other known good gauges. Also, verified on other vehicles I own with their TPMS screens and everything reads within .2 to .5 psi accuracy against my gauges.

It might be possible for the dealer to calibrate the screen readings but I haven’t heard of anyone else doing so. I trust my gauges more and set the tires to the pressure they show. The screen displays what it displays so long as I know how far it’s off I’m fine with it.

Other than for lower off-road pressures maybe once or twice a year during seasonal temperature changes I have to rest the RCP (Reference Cold Pressure) to avoid any unwanted TPMS warnings. I think besides being a minor annoyance it’s not that big a deal so long as you know you’ve set them based on the accuracy of your pressure gauges.