GF07.61-P-2008MIK ME-SFI Idle Speed Control Function
GF07.61-P-2008MIK ME-SFI Idle Speed Control Function
- refinement package
- as of model year 09
Idle speed control function requirements, general
^ Circuit 87M ON (engine control ON)
^ Engine running
^ Accelerator not operated
Idle speed control, general
The idle speed control regulates and stabilizes the idle speed according to operating conditions and engine load.
For the idle speed control, the ME-SFI control unit (N3/10) reads the following sensors and signals:
- Crankshaft Hall sensor (B70), motor speed
- Hot film MAF sensor (B2/5), engine load
- Coolant temperature sensor (B11/4)
- Clutch pedal switch (S40/3) (for manual transmission)
- Electric controller unit (VGS) (Y3/8), gear range over the engine compartment CAN (CAN C) (for automatic transmission)
- Comfort AAC control and operating unit (N22/7), air conditioning status over the interior CAN (CAN B) and engine compartment CAN
Idle speed control function sequence
The ME-SFI control unit regulates the idle speed through the throttle valve actuator (M16/6) and adapts the injection time of the fuel injection valves (Y62) according to variations in the air mass.
To assist the idle speed control, the ME-SFI control unit can shift the ignition angles of the ignition coils (T1) towards "retard" by up to 36° crank angle, or towards "advance" by up to 20° crank angle.
Adjusting the ignition angle enables a faster response than adjusting the throttle valve.
The ME-SFI control unit adjusts the idle speed in the following operating and engine load conditions:
^ Warm-up phase function sequence
^ Gear range "D" or "R" selection function sequence (for automatic transmission)
^ Clutch pedal operation function sequence (for manual transmission)
^ Refrigerant compressor cut-in (A9) function sequence
^ Battery undervoltage (G1) function sequence (for automatic transmission)
^ Purging function sequence
Warm-up phase function sequence
In the warm-up phase, the ME-SFI control unit controls the idle speed according to coolant temperature, in order to bring the catalytic converters more quickly up to operating temperature after engine start.
Additional function requirements in the warm-up phase are:
- Coolant temperature <40 °C
- Gear range "N" or "P" engaged
The ME-SFI control unit raises the idle speed to about 1100 to 1300 rpm for about 20 s.
After this time has elapsed, the idle speed is increased at a coolant temperature of < 70 °C in line with the temperature for approx. 50 seconds by approx. 50 to 100 rpm.
Gear range "D" or "R" function sequence (for automatic transmission)
When gear range "D" or "R" is engaged, a lower engine speed is set in order to reduce the tendency of the vehicle to creep forward. To do this, the ME-SFI control unit evaluates the "gear range engaged" CAN signal from the electric controller unit (VGS).
Clutch pedal operation function sequence (for manual transmission)
When actuating the clutch pedal the idle speed is stabilized. Clutch pedal operation is detected by the ME-SFI control unit through the clutch pedal switch.
Refrigerant compressor cut-in function sequence
So that engine idle speed will not fall when the refrigerant compressor is engaged, the comfort AAC control and operating unit first sends a CAN signal to the ME-SFI control unit.
The ME-SFI [ME] control unit adapts the idle speed appropriately.
Battery undervoltage function sequence (for automatic transmission)
If the ME-SFI control unit detects an undervoltage through "circuit 30", the idle speed is raised by about 100 rpm when gear range "D" or "R" is selected, until the ignition is switched off.
Purging function sequence
The idle speed control prevents any change in the engine speed due to purging.
Diagnosis
The basic setting of the idle speed can be read out and influenced using the DAS.
