Tire Monitor - Pressure Reads Lower On MID than Gauge
Tire Pressure Reads Lower on MID Than on Tire GaugeIf you set the tire pressures with a simple tire pressure gauge on a '05-06 RL or '06 TL at high altitude-say, Denver, CO-the tire pressures you'll see on the MID will be lower than what you set with your gauge. There's really nothing wrong with the TPMS that needs fixing; it's working just like it should. It's all about altitude and its relationship to air pressure.
The TPMS sensors are mounted inside the tires; they're designed to measure absolute pressure (the actual pressure inside the tires). A simple tire pressure gauge, on the other hand, is designed to measure the pressure difference between the tire pressure and the atmospheric pressure. At sea level, the atmospheric pressure is about 14.7 psi. But for every 1,000 feet you climb above sea level, it drops by about 0.5 psi. This drop in atmospheric pressure is actually not linear, but the rule of thumb of 0.5 psi for every 1,000 feet above sea level is close enough for the TPMS. So if you're in Denver-The Mile-High City (5,280 feet)-the atmospheric pressure is only about 12.2 psi. That's a 2.5 psi difference. If you set your front tire pressures to spec at 32 psi with a simple tire gauge, the MID would read about 30 psi.
As you drop down in elevation, the tire pressure readings on the MID and the tire pressure gauge readings will read closer together. At sea level, they'll read the same.