General Information

An exhaust brake is an optional auxiliary braking system that assists, but does not replace, the service brake system. The driver can use the exhaust brake, in combination with the accelerator and clutch pedal (if so equipped), to make maximum use of the exhaust brake in off-highway and mountain driving as well as in traffic or high-speed highway driving.

The exhaust brake is controlled by a dash-mounted rocker switch, shown in Fig., to help slow the vehicle when the accelerator is released.

To turn the exhaust brake on, press on the upper part of the rocker switch. When the exhaust brake switch is on, an amber light emitting diode (LED) illuminates inside the switch. When the panel lights are on, the EXHST BRK legend is backlit in green.

Fig. 1, Exhaust Brake Switch

The exhaust brake is only active when engine speed is between 1100 and 2700 rpm. Depressing the accelerator or clutch pedal deactivates the exhaust brake. The ABS system, when active, also deactivates the exhaust brake.

The exhaust brake is a butterfly valve mounted in the exhaust pipe. When the driver's foot is not on the accelerator pedal and the upper half of the exhaust brake switch is pressed in, with the amber light on the switch illuminated, an air cylinder shuts the butterfly valve, which restricts the flow of exhaust gases and retards the engine. This retarding action is carried through the engine and drivetrain, slowing the vehicle and reducing the need for frequent service brake applications.

Exhaust brakes are not intended for use as the primary braking system during vehicle operation.