GF07.16-P-3008OHL | CDI overrun mode, function | 5.5.08 |
ENGINE 642.9 in MODEL 221.0 as of Model Year 09 /Modification Year 08
ENGINE 642.9 in MODEL 221.1 as of Model Year 09 /Modification Year 08
General function requirements
Circuit 61 ON
Engine speed >700 rpm
Accelerator not operated
Common rail diesel injection (CDI) deceleration mode - general
The vehicle is in deceleration mode, when the drive wheels transfer torque to the engine via the transmission. The accelerator pedal sensor (B37) is not actuated.
To control the deceleration mode, the CDI control unit (N3/9) reads in the following sensors:
- Accelerator pedal sensor, accelerator pedal position
- Crankshaft Hall sensor (B70), motor speed
Function sequence
In deceleration mode at an engine speed over 1600 rpm and without depression of the accelerator pedal, actuation of the fuel injectors (Y76) is interrupted (zero quantity delivery). The CDI control unit also lowers the fuel pressure in the rail through the quantity control valve (Y94) and the pressure regulator valve (Y74).
If the accelerator pedal is depressed again or the engine speed falls below 1600 rpm, the CDI control unit re-actuates the fuel injectors and increases the fuel pressure in the rail via the quantity control valve and the pressure regulator valve.