Inspection of the Cab

Push the reset button on the dash-mounted air intake restriction indicator, if equipped.

With the ignition switch in the OFF position, check the air-pressure warning system.

If not previously drained, drain the air reservoirs using moderate brake applications until pressure in both reservoirs is less than 70 psi (483 kPa).
Turn the ignition to the ON position. The ICU will complete a full gauge sweep and bulb check, and the warning buzzer will sound. Ensure the BRAKE AIR lamp remains illuminated and the warning buzzer continues to sound after the gauge sweep is complete.

Check air governor cut-in and cut-out pressures.

Start the engine and ensure the BRAKE AIR lamp goes out and the buzzer silences when pressure reaches approximately 70 psi (483 kPa) in both air reservoirs.
The air governor should cut out at approximately 120 psi (827 kPa). For vehicles with an optional dryer reservoir module (DRM), the cut-out pressure is approximately 130 psi (896 kPa).
With the engine idling, apply the brake pedal several times. The air governor should cut in when pressure in the primary air reservoir (top air gauge) reaches approximately 100 psi (689 kPa).

Check air pressure build-up time.

With the air system fully charged, make one full brake application and note the air pressure reading on the primary air gauge.
Further reduce air pressure using moderate brake applications, then run the engine at governed rpm.
Note the time that the pressure reaches the previously noted reading on the primary air gauge, then note the time that the air pressure reaches cut-out pressure.
If it takes longer than 30 seconds to reach cut-out pressure after the primary air gauge passes the previously noted pressure (noted after one full brake application), eliminate any leaks or replace the air compressor before operating the vehicle.

Check air leakage in the system.

With the parking brake applied, the transmission out of gear, and the air system fully charged, release the service brakes and shut down the engine.
Wait one minute and note the air pressure drop in psi (kPa) per minute from the primary air reservoir.
If the pressure drop exceeds the limits shown in Table., eliminate any leaks before operating the vehicle.

Check the air pressure reserve.

With the engine still off, make one full brake application and observe the pressure drop on the primary air gauge. If pressure drops more than 25 psi (172 kPa), eliminate any leaks before operating the vehicle.

Table 1, Maximum Allowable Air Leakage

Maximum Allowable Air Leakage
Description	Pressure Drop: psi (kPa) Per Minute
Description	Released	Applied
Truck or Tractor Only	2 (14)	3 (21)
Truck or Tractor w/Single Trailer	3 (21)	4 (28)

Table 1, Maximum Allowable Air Leakage

Inspect the mirrors, window glass, and windshield for cracks or other damage.

Ensure that the horn, windshield wipers, and windshield washers are operating properly. These devices must be in good working order for safe vehicle operation.

Ensure the heater and defroster are operating properly.

Check the operation of all interior lights.

Turn on the headlights and leave them on. Ensure all equipped gauge bulbs illuminate in the dash message center.
Ensure all equipped driver control switches illuminate.
Ensure both turn signal indicator bulbs illuminate in the dash message center when the turn signal switch is activated.

Check the operation of all exterior lights. See Fig. or see Fig..

Activate the high-beam headlights and hazard warning lights.
Exit the cab and check that all exterior lights and reflectors are clean and intact.
Fig. 1, Exterior Lights (5700 models)
Fig. 2, Exterior Lights (4700 models)
Check that the brake lights, taillights, headlights, turn signals, marker lights, identification lights, and clearance lights are working properly.

Inspect the seat belts and tether belts.

Warning: Inspect and maintain seat belts. When any part of a seat belt system needs replacement, the entire seat belt must be replaced, both retractor and buckle side. Any time a vehicle is involved in an accident, and the seat belt system was in use, the entire vehicle seat belt system must be replaced before operating the vehicle. Do not attempt to modify the seat belt system; doing so could change the effectiveness of the system. Failure to replace worn or damaged seat belts, or making any modifications to the system, may result in personal injury or death.

Check the web for fraying, cuts, extreme dirt and dust, or for severe fading from exposure to sunlight, especially near the buckle latch plate and in the D-loop guide area.
Check operation of the buckle, latch, Komfort Latch or Sliding Komfort Latch (if equipped), web retractor, and upper seat belt mount on the door pillar. Check all visible components for wear or damage.
Check the seat belt and tether belt connection points and tighten any that are loose.

Check the fuel level in the fuel tank(s). To keep condensation to a minimum, fuel tanks should be filled at the end of each day.

Adjust the rearview and down view mirrors as necessary.

Test the service brakes.

With the engine running and air system fully charged, set the parking brake.
Put the vehicle in the lowest gear and gently attempt to move it forward. The vehicle should not move.
If the vehicle moves, the parking brakes are not operating correctly and must be repaired before the vehicle is operated.

Test the backup alarm.

Release the parking brake and put the transmission in reverse.
Move the vehicle slightly backward to ensure that the backup alarm is operating correctly.

4700, 5700, 4900, 6900 Driver's Manual

Table 1, Maximum Allowable Air Leakage

Table 1, Maximum Allowable Air Leakage

Fig. 1, Exterior Lights (5700 models)

Fig. 2, Exterior Lights (4700 models)