The function diagram for the brake shut-off valve includes the following:
• Engine Oil Temperature (EOT) sensor
• Speed Control Command Switches (SCCS)
• Injection Control Pressure (ICP) sensor
• Brake Control Pressure (BCP) sensor
• Engine brake switches
• Camshaft Position (CMP) sensor
• Accelerator Position / Idle Validation (APS/IVS) sensors
• Electronic Control Module (ECM)
• Brake pedal
• Brake shut-off valve
• Variable Geometry Turbocharger (VGT) actuator
• Exhaust Gas Recirculation (EGR) actuator
• ENGINE lamp (amber)
The brake shut-off valve controls pressure in the oil gallery of the high-pressure oil rail. When the engine brake is activated, the ECM provides power to activate the brake shut-off valve to allow oil from the injector oil gallery to flow to the brake oil gallery. High oil pressure activates the brake actuator pistons to open the exhaust valves.
The ECM removes the power from the brake shut-off valve to deactivate the engine brake. Residual brake gallery pressure initially bleeds from the actuator bore. When brake gallery pressure reaches 1000 psi, the brake pressure relief valve opens, and oil drains back to sump.
The brake shut-off valve consists of a solenoid and valve assembly and is located in the center of the high-pressure oil rail.
The ECM monitors the following criteria to make sure certain conditions are met.
• ABS (inactive)
• RPM (greater than 1200)
• APS (less than 5%)
• EOT (greater than 60 °C [140 °F])
• Idle validation
• Operator input switches (On/Off) (power selection – Low, Medium, High)