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

ENGINE 272.9 (except 272.982) in MODEL 204.0/2 as of model year 2009 

ENGINE 272.9 (except 272.983) in MODEL 212 

ENGINE 272.9 (except 272.984) in MODEL 207 

ENGINE 272.9 in MODEL 204.9 

ENGINE 273.9 in MODEL 207, 212 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87M ON (engine timing ON)
• Engine running
• Vehicle rolling
• Accelerator not operated
• Selector lever position "D" or "R" (for automatic transmission)
• Vehicle not in cruise control or DISTRONIC PLUS mode (vehicles with DISTRONIC PLUS)
• Not too high an exhaust temperature

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 sensors and signals:

• coolant temperature sensor (B11/4)
• accelerator pedal sensor (B37), accelerator pedal position
• crankshaft Hall sensor (B70), engine speed
• clutch pedal switch (S40/3) (with manual transmission)
• fully integrated transmission control controller unit (Y3/8), stage via the drive train CAN (CAN C) (for an automatic transmission)

Deceleration fuel shutoff, function 

In deceleration mode, the ME-SFI [ME] control unit switches off the injection valves (Y62) depending on coolant temperature, selected gear and engine speed, if the accelerator pedal is not actuated.

The injection valves are switched on again when the accelerator pedal is actuated.

If the clutch pedal is actuated for a manual transmission the deceleration fuel shutoff is broken off or suppressed.

The ME-SFI [ME] control unit also adjusts the valve overlap to its minimum value via the left and right intake camshaft solenoids (Y494, Y495) and the left and right exhaust camshaft solenoids (Y496, Y497). This ensures that an optimal conversion rate of the catalytic converters is more rapidly achieved.

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

In order to prevent a sudden rise in torque 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	MODEL 204	PE07.10-P-2714-97FAB
		MODEL 207	PE07.10-P-2714-97EAB
		MODEL 212	PE07.10-P-2714-97DAB
	Overview of system components motor electronics (ME-SFI) fuel injection and ignition system		GF07.61-P-9997MI