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

ENGINE 642.8 in MODEL 204, 207, 212, 218 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87M ON (Engine management ON)
• Engine runs
• Vehicle rolling
• Accelerator pedal not operated
• Selector lever position "D" or "R"
• Vehicle not in cruise control or DISTRONIC PLUS mode (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. In this way the braking effect of the engine is increased.

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

• Coolant temperature sensor (B114) (model 204, model 207, model 212), coolant temperature sensor (B11/4) (model 218)
• Accelerator pedal sensor (B37), accelerator pedal position
• Crankshaft Hall sensor (B70), engine rpm
• Fully integrated transmission controller unit (Y38) (with code 427 (7-speed automatic transmission) or code 421 (9-speed automatic transmission), gear range via the 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 rails by means of the quantity control valve (Y94) and the pressure regulating valve (Y74).

If the accelerator pedal is depressed again or the engine speed falls below 1100 rpm, the CDI control unit re-actuates the fuel injectors and increases the fuel pressure in the rails via the quantity control valve and the pressure regulating valve.