2006-2010 Suzuki DF150 / DF175 4-Stroke Outboards Service Manual, Page 85Get this manual
ENGINE CONTROL SYSTEM
IAC VALVE The IAC valve uses stepper type motor The IAC valve is installed on the intake manifold The IAC valve controls the volume of bypass air to stabilize the idlingtrolling speed The transistor driving the IAC is inside the ECM and turns ONOFF when signal (command) is received from the CPUThis signal operates the stepper motor inside the IAC valve, causing it to be driven equal to the number of command signal stepsThrough this procedure, the system is able to attain very precise target idlingtrolling speed The stepper motor rotates by means of magnetic attraction between the stator and rotorMore specifically, shifting the stator excitation in State (1) of the illustration below to that in State (2) will develop magnetic torque to cause the rotor to rotate and then stabilize in State (3)(The illustration below shows the operating principle of simple stepper motorThis example differs slightly from the 2-phase excitation method used in the actual application)This operation is repeated equal to the number of command signal steps from the ECM resulting in rotation of the rotorWith the screw shaft installed, this rotation is converted to linier motion of the valve pintle that changes the volume of IAC air flow Battery voltage is applied to the center tap of each coil through the ECM main relay when the ignition switch is turned onEach coil end connects to one of the ECM terminals "IAC 1-4"The terminal voltage at ECM terminals "IAC 1-4" is MAX when current flows and battery voltage at all other times3 +12 ECM Gr 1Valve pintle 2Screw shaft 3Rotor 4Coil 5Bearing Air flow IAC valve WB RG WBl RY 55 58 57 56 IAC1 IAC3 IAC4 IAC2