GF07.16-P-3002OHL | CDI idle speed control, 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
Accelerator not operated
No deceleration mode
Common rail diesel injection (CDI) idle speed control - general
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 in information from the following components:
- "KOMP_AUS" (refrigerant compressor (A9) deactivated), from the AAC control unit (N22/1) through the interior CAN, central gateway control unit (N93) and chassis CAN
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- Intake air mass, from the LH hot film MAF sensor (B2/6) and RH hot film MAF sensor (B2/7)
- Intake air temperature, from intake air temperature sensor (B2/6b1) and intake air temperature sensor (B2/7b1)
- Fuel pressure in the rail, through the rail pressure sensor (B4/6)
- Coolant temperature, from the coolant temperature sensor (B11/4)
- Accelerator pedal position, from the accelerator pedal sensor (B37)
- Engine speed from the crankshaft Hall sensor (B70)
- Selector lever position "P", "N" or "D", from the fully integrated transmission control unit (VGS) (Y3/8n4)
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Function sequence
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 then regulates the fuel pressure in the rail through the quantity control valve (Y94), and the injection quantity through actuations of the fuel injectors (Y76).
The fuel pressure in the rail and injection timing of the fuel injectors gives the injection quantity.