Deceleration fuel shutoff, function - GF07.10-P-1014MM

ENGINE 276.8 in MODEL 207, 212 as of model year 2014 

ENGINE 276.8 in MODEL 218 as of model year 2015 

ENGINE 276.9 in MODEL 204, 207, 212 (except 212.095), 218 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87M (engine timing ON)
• Engine runs
• Vehicle rolling
• Accelerator pedal not operated
• Gear range "D" or "R" is engaged
• Gear range "N" engaged (for a stationary or a rolling vehicle)
• Vehicle not in CC mode, DISTRONIC PLUS mode (for code 233 (DISTRONIC PLUS), Active Blind Spot Assist mode (for code 237 (Active Blind Spot Assist) or Active Lane Keeping Assist mode (for code 238 (Active Lane Keeping Assist))
• Not too high an exhaust temperatures

Deceleration fuel shutoff, general 

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 [ME] control unit (N3/10) performs a deceleration fuel shutoff dependent on the following sensors and signals:

• Coolant temperature sensor (B11/4) (model 204, 207, 212), coolant temperature sensor (B11/4) (model 218)
• Accelerator pedal sensor (B37), accelerator pedal position
• Crankshaft Hall sensor (B70), engine RPM
• Fully integrated transmission controller unit (Y3/8), stage via the drive train CAN (CAN C)

Deceleration fuel shutoff, function sequence 

In deceleration mode, the ME-SFI [ME] control unit switches off the fuel injectors (Y76) dependent on coolant temperature, engaged gear and engine speed, if the accelerator pedal is not actuated.

The fuel injectors are switched on again when the accelerator pedal is operated. The ME-SFI [ME] control unit also uses the left and right intake camshaft solenoids (Y49/4, Y49/5) and the left and right exhaust camshaft solenoids (Y49/6, Y49/7) to adjust the camshafts to a position with reduced valve overlap. This allows secure combustion without misfires.

After deceleration fuel shutoff, the ME-SFI [ME] control unit enriches the fuel/air mixture by briefly lengthening the injection period in order to relieve the catalytic converters of enriched oxygen. In order to prevent a sudden torque rise when combustion is restarted after a deceleration fuel shutoff, the ME-SFI [ME] control unit briefly shifts the ignition angles of the ignition coils (T1) 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 (afterburning). The heat so generated can overheat the catalytic converters.