The external gauge agreed with OEM tire pressure sensors. The external gauge agrees with another vehicle’s TPMS reading.
Then Costco installed a new set of sensors in a second wheel set that now reads +4psi high relative to the external gauge. There’s a vehicle configurable calibration factor that’s now set wrong with the onboard TPMS.
(1) New rims with winter tires. Costco installed new pressure sensors for $175.56
(2) OEM rims with OEM pressure sensors. Costco installed new tires in the same OEM size and charged for $11.96 tire pressure service pack (metal nut, rubber grommet, washer, and valve core )
The first service set (1) I figured it was a sensor problem. Set (2) still has the OEM pressure sensor. Before Costco touched them, the dash readout agreed with the external tire pressure sensor. After Costco touched set (2), the truck’s TPMS readings are since reading +4 psi high vs the external tire pressure sensor.
These two experiences suggest there is a way to calibrate the TPMS system’s bias.
I bought my TPMS (snow tires) from the Ford Dealer.
Ford Performance Tire Pressure Monitoring System Kit Of Four Sensors And Activation Tool
Part Number:
M-1180-433MHZ
It was $120 and included the resetting tool. This was much cheaper than buying the sensors alone and they were OEM.
Yes it was cheaper than COSTCO
Another point - your tires will run above the cold tire pressure within minutes of driving down the road since your tires warm up. +4 psi is normal for winter tires once they warm up. Set the cold at 42psi (on my ER), and on the highway, they run 45-46psi. They cool down pretty fast and by the time you check them with your gauge, they are likely nearly cold again.
I like to under inflate my winter tires a bit... I set them to 37PSI cold. This has been proven to give better traction. The negative side of that is there is more resistance so you lose a bit of range. For me, I don't travel long distances, so it's worthwhile.
It could be worse...after an OTA update early in my ownership, this is what happened to my tire pressure reading on FordPass...well it was a hot summer: