Idle Speed Control
The ECM determines idle speed by controlling an idle speed actuator (dual winding rotary actuator) ZWD 5.
The basic functions of the idle speed control are:
- Control the initial air quantity (at air temperatures <0 C, the EDK is simultaneously opened)
- Variable preset idle based on load and inputs
- Monitor RPM feedback for each preset position
- Lower RPM range intake air flow (even while driving)
- Vacuum limitation
- Smooth out the transition from acceleration to deceleration
Under certain engine operating parameters, the EDK throttle control and the idle speed actuator (ZWD) are operated simultaneously.This includes All idling conditions and the transition from off idle to load.
As the request for load increases, the idle valve will remain open and the EDK will supply any additional air volume required to meet the demand.
Emergency Operation of Idle Speed Actuator:
If a fault is detected with the idle speed actuator, the ECM will initiate failsafe measures depending on the effect of the fault (increased air flow or decreased air flow).
If there is a fault in the idle speed actuator/circuit, the EDK will compensate to maintain idle speed. The EML lamp will be illuminated to inform the driver of a fault.
If the fault causes increased air flow (actuator failed open), VANOS and Knock Control are deactivated which noticeably reduces engine performance.