Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014MMY

Engine 157.9, 278.9 in model 166 

as of model year 2016 

Engine 157.9, 278.9 in model 292 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87M (engine management ON)
• Engine runs
• Vehicle rolling
• Accelerator not operated
• Gear range "D" or "R" is engaged
• None of the following driver assistance systems in use:
  • Cruise control
  • DISTRONIC PLUS (with CODE 233 (DISTRONIC PLUS))
  • Active Blind Spot Assist (with CODE 237 (Active Blind Spot Assist))
  • Active Lane Keeping Assist (with 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 depending on the following signals:

• Coolant temperature sensor (B11/4), coolant temperature
• Accelerator pedal sensor (B37), accelerator pedal position
• Crankshaft Hall sensor (B70), engine rpm
• Fully integrated transmission control unit (Y3/8n4), gear range via 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.

	Electrical function schematic for deceleration fuel shutoff		PE07.10-P-2714-97NBB
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MNG