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

Engine 276.8 in model 213, 238 

up to model year 2021 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87M (Engine management ON)
• Engine runs
• Accelerator not operated
• Gear range "D" or "R" is engaged
• Gear range "N" engaged (for a stationary or a rolling vehicle)
• Vehicle is not in cruise control mode
• Not too high an exhaust temperatures

The "Engine running" function requirements include all function sequences of the fuel low pressure and fuel high-pressure circuit, as described in the "Fuel supply" function.

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)
• Accelerator pedal sensor (B37), accelerator pedal position via powertrain control unit (N127) and drive train CAN (CAN C1)
• Crankshaft Hall sensor (B70), engine RPM
• Fully integrated transmission control unit (Y3/8n4), gear range via drive CAN

Deceleration fuel shutoff, function sequence 

In overrun mode, the ME-SFI [ME] control unit switches off the fuel injectors for cylinders 1 to 6 (Y76/1 to Y76/6) depending on the 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 extending the injection period in order to protect the catalytic converters (three-way catalytic converters) from enriched oxygen.

To prevent a sudden torque rise when combustion is resumed after an overrun mode fuel shutoff, the ME-SFI [ME] control unit briefly adjusts the ignition angles of the ignition coils of cylinders 1 to 6 (T1/1 to T1/6) in the direction "retarded".

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-2714-97DBF
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MND