Overrun Mode Fuel Shutoff, Function - GF07.10-S-1014TRJ

Engine 274 in model 447.6/7 

with code XM0 (Facelift) 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87M ON (Engine management ON)
• Engine running.
• Vehicle rolling.
• Accelerator not actuated.
• Selector lever position "D" or "R" (with automatic transmission)
• Clutch pedal not actuated (for manual transmission).
• Vehicle not in CC mode (with code MS1 (CC))
• Exhaust temperature in target area

Deceleration fuel shutoff, general 

The ME-SFI [ME] control unit (N3/34) performs a deceleration fuel shutoff dependent on the following sensors and signals:

• Coolant temperature sensor (B11/21), coolant temperature
• Accelerator pedal module (B37/4), accelerator pedal position
• Crankshaft Hall sensor (B70/2), engine rpm
• Clutch pedal switch (S40/3) and clutch pedal switch (S40/6) (with manual transmission), clutch pedal status
• Fully integrated transmission control (VGS) electric controller unit (N15/11) (Automatic transmission with code G42 (7G-TRONIC PLUS)), drive range
• Fully integrated transmission control (VGS) electric controller unit (N15/15) (Automatic transmission with code G43 (9G-TRONIC)), drive range
• Electronic Stability Program (ESP) control unit (N30/4) for wheel speed

Deceleration fuel shutoff, function sequence 

In deceleration mode, the ME-SFI [ME] control unit switches off the fuel injectors (Y62) 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 adjusts the valve overlap to its min. value via the intake camshaft solenoid (Y49/10) and the exhaust camshaft solenoid (Y49/11). This ensures that an optimal conversion rate of the catalytic converter is more rapidly achieved.

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 reestablished after deceleration fuel shutoff, the ignition timing is briefly adjusted towards "retarded" by the ME-SFI [ME] control unit.

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 of the catalytic converter.