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Home >> Ford >> 2000 >> ZX2 Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> Theory and Operation >> Engine Controls - Theory & Operation - EEC-V (Gasoline) >> Air Induction Systems >> Supercharger (5.4L - F150 Lightning) >> Supercharger Bypass System

Supercharger Bypass System

Supercharger Bypass (SCB) system allows high pressure air at outlet of supercharger to vent back to inlet side of supercharger. This equalizes pressure and eliminates boost for times when supercharger function is not required. Descriptions of supercharger bypass system components are as follows:

  1. Vacuum Bypass Actuator

    During normal operation engine vacuum is applied to upper port of vacuum bypass actuator. Lower port of vacuum bypass actuator references air pressure in clean air tube, cancelling out any pressure difference in intake air system. Actuator opens during engine high vacuum conditions (bypassing supercharger). As throttle is opened and engine vacuum decreases, vacuum bypass actuator closes to allow supercharger to pressurize air in intake manifold.
  2. SCB Solenoid/Thermactor Air Control Solenoid

    SCB solenoid is used to control intake manifold vacuum to vacuum bypass actuator. The SCB solenoid is de-energized during normal operating conditions. The Powertrain Control Module (PCM) will transmit an output signal to activate SCB solenoid to apply stored vacuum from vacuum reservoir assembly to vacuum bypass actuator when an undesirable condition occurs in the engine. Once engine condition is corrected SCB solenoid will be deactivated by PCM allowing engine intake manifold vacuum to control vacuum bypass actuator.
  3. Vacuum Reservoir Assembly

    Vacuum reservoir assembly stores vacuum that is applied to the vacuum actuator when a condition such as overheating or critical sensor failure is generated.