Driver Controls and Instruments Suspension) system uses a height sensor mounted be- tween the frame and the drive axle housing as well as other sensors to provide frame height information to a control unit mounted inside of the cab. The electronic control unit quickly lowers or raises the frame height, as necessary. Altering the height of the frame while the vehicle is parked can be performed using a hand-held remote control unit. See Chapter 7 , under the heading "Air Brake System," for instructions on the use of the trailer air supply valve and parking brake valve.
Parking Brake Control Lever On Vehicles With Hydraulic Brakes If the vehicle is equipped with hydraulic brakes, a park- ing brake control lever is located on the cab floor near the gear shift lever. To apply the parking brake, depress the brake pedal, then pull up on the parking brake lever. To release the parking brake, depress the brake pedal and push the parking brake lever all the way down. Turning the knob counterclockwise decreases the effort needed to move the lever. WARNING Stand away from the rear of the vehicle when rais- ing or lowering the height of the frame. The ECAS system operates quickly, and contact could result in personal injury.
For the optional automatic function to work, the vehicle must be equipped with rear axle air suspension and ABS. Automatic Traction Control is recommended for optimal vehicle traction control. If the parking brake does not hold the vehicle securely, depress the brake pedal and release the parking brake. Turn the knob on the end of the lever clockwise to in- crease the parking brake application. Parking Brake Control Valve Vehicles Without Trailer Air Brake Hookup NOTE: Turning the knob clockwise will also in- crease the effort needed to apply or release the parking brake lever. A diamond-shaped knob in the control panel operates the parking brake control valve.
When the knob is out, the truck’s spring parking brakes are applied. When the knob is in, the parking brakes are released. Before the parking brakes can be released, air pressure in either brake system must be at least 65 psi (447 kPa). If the parking brake still doesn’t securely hold the ve- hicle (after adjustment), check the brake lining thick- ness. For instructions, see Group 42 of the Business Class Trucks Maintenance Manual. 3.15