If your vehicle has air brakes, this gage shows the air pressure for both your front and rear brake systems.

If the needle on the gage indicates that the air pressure is below 60 psi (415 kPa), the low air warning light will come on. An alarm will also sound if this happens.

The bottom yellow pointer shows the pressure available for the front secondary system, while the top white pointer shows pressure for the rear primary system. There should be no more than 4 psi (28 kPa) difference showing between the systems.

Don't drive until both pointers are showing at least 120 psi (827 kPa), so you'll have enough air if you need to apply your brakes.