Intake Valve Lift Control System Operation

The intake valve lift control system is controlled by the engine control module (ECM). The ECM sends a signal to the rocker arm actuator solenoids in order to control the amount of oil flow and pressure to the switching rocker arms. This oil is routed through a control passages to dual-feed hydraulic lash adjusters and then into the rocker arms. Rocker arms can switch between low-lift and high-lift cam profiles when the oil pressure in the control passage is changed by the ECM commands. Control oil pressure operates a latching pin internal to each switching rocker arm which results in the rocker arm following either the low or high lift cam profile. All switching occurs when the cams are on base circle, with no valve lift.

When high-lift operation is required, the control passage oil pressure is low. This allows the latching pins to remain extended and the rocker arms contact and follow the high-lift cam profiles. When low-lift operation is required, the control passage oil-pressure is increased. This retracts the latching pins internal to the switching rocker arms and allows the rocker arms to follow the low-lift cam profile.