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

ENGINE 651.9 in MODEL 166 as of model year 2016 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87M (engine management ON)
• Engine runs
• Vehicle rolling
• Accelerator not operated
• Selector lever position "D" or "R"
• Vehicle not in cruise control or DISTRONIC PLUS mode (vehicles with DISTRONIC PLUS)

Deceleration fuel shutoff, general 

Deceleration fuel shutoff causes the drive wheels to transmit a braking torque to the engine via the transmission. This increases the braking effect of the engine (engine brake).

The CDI control unit (N3/9) performs a deceleration fuel shutoff as specified by the following sensors and signals:

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

Deceleration fuel shutoff, function sequence 

If the accelerator pedal is not actuated (zero quantity delivery), deceleration mode is triggered. The CDI control unit switches off the fuel injectors (Y76) in deceleration mode dependent on the coolant temperature, the engaged gear and at an engine speed >1600 rpm.

The CDI control unit also lowers the fuel pressure in the rail over the pressure regulating valve (Y74). Upon operation of the accelerator pedal or a drop in the engine rpm to < 1600, the CDI control unit again actuates the fuel injectors and increases the fuel pressure in the rail via the quantity control valve (Y94) or the pressure regulating valve, depending on the fuel pressure in the rail.