Nissan Throttle Opener Control System (T.O.C.S.) - Description & Operation Chart

This is page EF & EC-28 from a Nissan service manual covering the Exhaust Emission Control section, specifically the Throttle Opener Control System (T.O.C.S.). The description explains that the throttle opener slightly opens the carburetor's throttle valve during deceleration, when high manifold vacuum would otherwise leave the mixture too lean for normal combustion, causing unburned hydrocarbon (HC) emissions. By supplying an adequate combustible mixture during deceleration, the system dramatically reduces HC emissions. A schematic diagram shows the system layout including the carburetor, primary throttle valve, throttle opener servo diaphragm, vacuum control valve, altitude corrector, solenoid, ignition switch, battery, function check connector (with G/R and B wires), speed detecting switch (ON below 10 km/h / 6 MPH), amplifier (M/T), and inhibitor switch for A/T (ON in "N" or "P"). An operation table details system logic: on manual transaxles, in any gear, the solenoid is ON and T.O.C.S. is not operated below 10 km/h (6 MPH), and OFF/operated above that speed; on automatic transaxles, the solenoid is ON (system not operated) in "N" or "P" at any speed, and OFF (operated) in other gear positions. The diagram reference is SEC25.