Cartwaveforms > actuators > idle speed control valve > Idle Speed Control Valve (Rotary)
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Idle Speed Control Valve (Rotary) Waveform Notes
The rotary Idle Speed Control Valve (ISCV) will have 2 or 3 electrical connections, with a voltage supply at battery voltage and either a single or a double switched earth path. The rate at which the earth path is switched is determined by the Electronic Control Module (ECM) to maintain a prerequisite speed according to it’s programming.
The valve will form an air by-pass past the throttle butterfly, to form a controlled air bleed within the induction tract. If the engine has an adjustable air by-pass and an ISCV, it may require a specific routine to balance the two air paths. The rotary valve will have the choice of either single or twin earth paths, the single being pulled one way electrically and returned to its closed position via a spring; the double switched earth system will switch the valve in both directions. This can be monitored on a dual trace oscilloscope. As the example waveform shows the earth path is switched and the resultant picture is produced. Probing onto the supply side will produce a straight line at charging voltage and when the earth circuit is monitored a square wave will be seen. The frequency can also be measured.
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