Chevrolet Low Cab Forward 6.7L 2022 Owner's Manual page 211

210 Vehicle Care
Air Dryer
Change the desiccant and the filter s rubber
parts of the air dryer at the intervals
specified by the Maintenance Schedule. Take
care to ensure that the drain port is not
blocked or obstructed by foreign material.
The air dryer removes moisture and oil that
is present in the vehicle s air piping by
means of an inside desiccant.
If water and oil is discharged when the
drain tap on the air tank is opened for
checking, the desiccant has deteriorated and
needs to be changed. Desiccant replacement
requires disassembling of the relevant
components, so you should have it done by
the nearest GM dealer.
Brake Air Pressure
1. Check the brake air pressure gauges to
see that the primary and secondary air
systems are charged with air to proper
pressures.
2. Confirm the parking brake is fully
engaged. There are two air tanks on
your vehicle. One is behind the rear axle
and the other is between the front and
rear axles. Pull the lanyard attached to