System description The expanded EDC control box 51.11615–7169 contains the following functions: EDC fault diagnosis with LED and flashcode Idle speed adjustment Conversion of 4–20 mA input signal into a voltage signal Galvanic separation of the 4–20 mA input signal from the EDC control unit Simulation of the idle switch if the 4–20 mA triggering system is used Communication with the MAN-Cats checking and diagnostic computer is possible via an ISO interface also integrated in the terminal box. The control unit, with its program adapted to the engine model concerned, determines the optimum setting of the control rod from all the measured values.
To ensure the vehicle can still be driven to the nearest workshop in the event of one or several sensors failing, an emergency drive function is integrated in the control unit which, depending on the situation, makes it possible to continue driving with restricted functions. The idle speed is exactly maintained by means of the idle speed governor as long as the engine output is sufficient for this. The regulated idle speed can be altered within certain limits. The idle speed set ex works is 600 rpm. However, it can be varied via the EDC operating element in the range from 600 to 750 rpm. Starting-fuel delivery is output when either a lower start recognition speed is exceeded.
The starting-fuel delivery and cold idle speed are limited as a function of the coolant temperature to avoid impermissible smoke emission and unnecessary revving of the engine after starting. 9