GF07.61-P-4019MOS ME-SFI Deceleration Fuel Shutoff, Function

GF07.61-P-4019MOS ME-SFI Deceleration Fuel Shutoff, Function
- as of model year 09


Function requirements for deceleration fuel shutoff, general points
^ Circuit 87M ON (engine control ON)
^ Engine running
^ Vehicle rolling
^ Accelerator not operated
^ Selector lever position "D" or "R"
^ Vehicle not in cruise control or Distronic Plus mode (if Distronic PLUS installed)
^ Not too high an exhaust temperature

Deceleration fuel shutoff, general points
Deceleration fuel shutoff in deceleration mode of the engine has the following tasks:
- Increasing the braking effect of the engine
- Reducing fuel consumption
- Improving exhaust characteristics

The ME-SFI (N3/10) control unit performs a deceleration fuel shutoff according to the following sensors and signals:
- Coolant temperature sensor (B11/4)
- Accelerator pedal sensor (B37), accelerator pedal position
- Crankshaft position sensor (L5), motor speed
- ETC control unit (N15/3), shift stage over the drive train CAN (CAN C)

Deceleration fuel shutoff function sequence
In deceleration mode, the ME-SFI control unit shuts off the fuel injection valves (Y62) according to coolant temperature, engaged gear and engine speed, if the accelerator pedal is not actuated. The fuel injection valves are switched on again when the accelerator pedal is operated.

After deceleration fuel shutoff, the ME-SFI control unit enriches the fuel-air mixture by briefly extending the injection time, in order to protect the catalytic converters from enriched oxygen.

To avoid a sudden rise in torque when combustion is restarted after a deceleration fuel shutoff, the ME-SFI control unit briefly shifts the ignition angles of the ECI ignition modules for the RH and LH cylinder banks (N92/1, N92/2) towards "retard".

Deceleration fuel shutoff is disabled when exhaust temperatures are too high, since the high oxygen content occurring in the exhaust during a deceleration fuel shutoff could cause increased oxidation of carbon monoxide and hydrocarbon (after burning). The heat so generated can overheat the catalytic converters.