CDI idle speed control, function - GF07.16-P-3002P

ENGINES 642 in MODELS 209.3/4, 211.2, 219.3, 211.0/6 

ENGINES 642.9 in MODEL 461.3, 463.3 

ENGINES 642 in MODEL 203.0, 164.8, 251.0, 203.2, 164.1, 251.1 up to model year 2008/YoM 07 

Idle speed control keeps the idle speed of the engine constant at approx. 700 RPM. The CDI control unit (N3/9) does this by reading the following information:

• "COMP_OFF" (refrigerant compressor (A9) deactivated) from the EIS [EZS] control unit (N73) via the Controller Area Network bus Class C (engine compartment) (CAN-C) (except model 461)
• The fuel pressure of the rail via the rail pressure sensor (B4/6)
• Coolant temperature from the coolant temperature sensor (B11/4)
• The position of the accelerator pedal via the accelerator pedal sensor (B37)
• The engine speed via the crankshaft Hall sensor (B70).
• The selector lever position "P" or "N" from the electronic selector lever module control unit (N15/5) (models 203, 209, 211, 219, 461, 463) or DIRECT SELECT gear selector switch (S16/13) (models 164, 251) via CAN-C

The CDI control unit uses the signal from the crankshaft Hall sensor to calculate the engine speed (actual value) and compares this actual value with the respective specified value stored in the performance map, which is dependent on other variables and messages. The CDI control unit subsequently regulates the fuel pressure in the rail via the quantity control valve and the pressure regulator valve (Y74) and the injection time via actuation of the fuel injectors (Y76).

The fuel pressure in the rail and injection timing of the fuel injectors gives the injection quantity.