How to Operate the Engine Brakes
The engine brake controls allow the driver to turn the engine brakes on and off and select a Low, Medium, or High level of braking. There is very little audible difference when the engine brakes are activated in either the medium or the high position.
The "Low" setting activates braking on three cylinders, yielding about one-third engine braking horsepower.
The "Medium" setting activates all six cylinders, supplying about two thirds engine braking horsepower.
The "High" setting activates all six cylinders along with varied EGR control, supplying full engine brake horsepower.
Engine Brake Activation Conditions
The engine braking system only permits fully automatic operation when the following conditions are met:
Engine brake is activated on.
An engine brake level (Low/Med/High) is selected.
Vehicle meets the programmed minimum speed.
The clutch pedal is depressed.
The accelerator pedal is at zero percent activation.
The Detroit Diesel Electronic Control® (DDEC®) system will deactivate the engine brake system when the engine speed falls below a preset rpm or when the vehicle slows down to a preset speed. This prevents stalling the engine. The engine brakes can also be used with vehicle cruise control turned ON. Some systems may be programmed to activate themselves only when the brake pedal is pressed.
During normal vehicle operation the engine brakes may go into a self-activation mode to assist in maintaining proper temperatures during an active DPF regeneration, this mode is called Thermo Coast. While the vehicle is operating in Thermo Coast the operator may notice that the engine brakes are active even though the engine brake selection is off.
Anti-Lock Braking Systems (ABS)
The ABS has the ability to turn the engine brake OFF if a wheel-slip condition is detected. The engine brake will automatically turn itself ON once the wheel slip is no longer detected.
Clutch Pedal and Throttle Position Controls
Engine brakes have two additional controls, one activated by the position of the clutch pedal and the other activated by the position of the throttle. These controls permit fully automatic operation of the engine braking system.
Engine Brake and Cruise Control
Engines with cruise control and engine brake function enabled can operate the engine brake automatically while in cruise control. If the Cruise Control/Engine Brake function is turned ON in the DDEC® system programming, the engine brake will come on low when the set road speed increases above cruise set speed. If vehicle speed continues to increase, the DDEC® system will increase the engine brake's braking power progressively. When the vehicle returns to the set cruise speed the engine brake will turn off.