EDK Feedback Signal Monitoring & EDK Failsafe Operation

The EDK provides 2 separate signals from 2 integral potentiometers (pot 1 and pot 2) representing the exact position of the throttle plate. EDK pot No. 1 provides the primary throttle plate position feedback. As a redundant safety feature, pot No. 2 is continuously cross checked with pot No. 1 for signal plausibility. If plausibility errors are detected between pot No. 1 and pot No. 2, ME 7.2 will calculate the inducted engine air mass (from HFM signal) and only utilize the potentiometer signal that closely matches the detected intake air mass. The ME 7.2 uses the air mass signalling as a virtual potentiometer (pot No. 3) for a comparative source to provide failsafe operation. If ME 7.2 cannot calculate a plausible conclusion from the monitored pots (1 or 2 and virtual 3) the EDK motor is switched off and fuel injection cut out is activated (no failsafe operation possible).

The EDK is continuously monitored during all phases of engine operation. It is also briefly activated when motor is initially switched on as a pre-flight check to verify its mechanical integrity (no binding, appropriate return spring tension, etc). This is accomplished by monitoring both the motor control amperage and the reaction speed of the EDK feedback potentiometers. If faults are detected, the EDK motor is switched off and fuel injection cut off is activated (no failsafe operation possible). The engine does, however, continue to run extremely rough at idle speed. When a replacement EDK is installed, the ME 7.2 adapts to the new component (required amperage draw for motor control, feedback pot tolerance differences, etc). This occurs immediately after the next cycle for approximately 30 seconds. During this period of adaptation, the maximum opening of the throttle plate is 25 percent.