Centinel System – Repair Manual – 020-999   Vehicle Braking – Overview

Signature and ISX engines are equipped with the Intebrake™ system (engine brakes). The Intebrake™ system is optional on QSX engines.

Engine brakes use the energy of engine compression to provide vehicle retardation by converting the engine to an energy-absorbing device to reduce vehicle speed. This is accomplished by a hydraulic circuit that opens the exhaust valves near the end of the compression stroke.

Engine brakes provide the maximum retarding power at rated speed; therefore, gear selection is important.

The amount of braking power available on Signature, ISX, or QSX engines is up to 600 hp. Braking power is managed by the Intebrake™ system (engine brakes).

Engine brake controls consist of the following:

• A six-position selector switch or a three-position selector switch
• An on/off switch
• A clutch switch
• A throttle sensor
• A service brake pressure switch.

Other switches for cruise control that affect engine brake operations are:

• Cruise control ON/OFF and SET/RESUME switches (if the engine brakes in cruise control feature is turned off)
• Service brake air pressure switch.

Engine brakes can operate while cruise control is turned on. Refer to Programmable Features in this section.

The six-position selector switch is located next to the on/off switch in the cab, and allows you to select the retarding power from brake positions 1 to 6.

The engine brake level specifications (six-position selector switch):

Position 1 = 17-percent engine braking power

Position 2 = 33-percent engine braking power

Position 3 = 50-percent engine braking power

Position 4 = 67-percent engine braking power

Position 5 = 83-percent engine braking power

Position 6 = 100-percent engine braking power.

NOTE: For OEMs that use a three-position selector switch, the engine brake level specifications are:

Position 1 = 33-percent engine braking power

Position 2 = 67-percent engine braking power

Position 3 = 100 percent engine braking power.

Signals from the on/off switch, the clutch switch, the throttle sensor, and the cruise/PTO switches are fed into the electronic control module (ECM).

NOTE: Any one of these switches can deactivate the engine brakes. If the engine brakes in cruise control feature is turned on, the cruise control/PTO switches will not deactivate the engine brakes.

The ECM then electronically enables or disables the engine brakes.

NOTE: Engine brakes can not be enabled:

1. When cruise control is active and if the engine brakes in cruise control feature is turned off
2. When engine speed drops below 850 rpm, or 30 mph
3. When an electronic fault code is active.

The “throttle sensor” is part of the accelerator pedal assembly located in the cab and will deactivate the engine brakes when depressed.

The “clutch switch” uses the motion of the clutch linkage to deactivate the engine brakes when the clutch pedal is depressed. Depressing the clutch while in cruise control will disengage the cruise control.

The “service brake pressure switch” is attached to the service brake air supply line.

Applying the service brakes while in cruise control will disengage the cruise control and enable the engine brakes.

If the pedal activated engine brake feature is enabled, the service brake pedal must be tapped before the engine brakes will be activated.

Idle the engine 3 to 5 minutes at approximately 1000 rpm to warm the engine before activating the engine brakes. Do not operate the engine brakes until the engine oil temperature is above 30°C [86°F].

To activate the engine brakes, switch the on/off switch to the ON position. Once activated, the operation of the engine brakes is fully automatic.

NOTE: Refer to the appropriate pages in this section for specific information about engine brake operation under certain road conditions.

WARNING  Do not use the engine brakes while bobtailing or pulling an empty trailer. With the engine brakes in operation, wheel lockup can occur more quickly when the service brakes are applied, especially on vehicles with single-drive axles.

Make sure the engine brakes are switched to the OFF position when bobtailing or pulling an empty trailer.

CAUTION  The engine brakes are designed to assist the vehicle’s service brakes in slowing the vehicle to a stop.

Remember, service brakes will be required to bring the vehicle to a stop.

The ECM will disable the engine brakes when engine rpm is below 850 rpm or when an electronic fault code is active.

CAUTION  Do not operate the engine if the engine brakes will not deactivate. To do so will cause severe engine damage.

If the engine brakes will not shut off, shut off the engine immediately.