Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014KJ
ENGINE 281.910 in MODEL 453.0/3/4
Function requirements for deceleration fuel shutoff, general points
- Circuit 87 (Engine management ON)
- Engine runs
- Vehicle rolling
- Accelerator pedal not operated
- Selector lever position "D" or "R" (for code 429 (twinamic))
- Vehicle is not in cruise control mode
- Not too high an exhaust temperatures
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
- Crankshaft position sensor (L5), engine speed
- DKG control unit (N15/13) (for code 429 (twinamic)), gear range via drive train CAN (CAN C)
- Clutch pedal switch (S40/3) (for code 410 (5-speed manual transmission)), status via middle SAM control unit (N10/10) and interior CAN (CAN B)
- CC/variable speed limiter switch (S40/4s6), status over steering wheel clock spring contact (A45/1)
Deceleration fuel shutoff, function sequence
In decel mode the ME-SFI [ME] control unit switches off cylinder 1 injection valve (Y62/1) to cylinder 3 injection valve (Y62/3) dependent on the coolant temperature, the engaged gear and the engine rpm, if the accelerator pedal is not depressed.
The injection valves are switched on again when the accelerator pedal is actuated.
If the clutch pedal is actuated the deceleration fuel shutoff is broken off or suppressed.
The ME-SFI [ME] control unit also adjusts the intake camshaft into a position with reduced valve overlap by means of the variable camshaft position valve (Y49/10). This allows secure combustion without misfires.
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 any sudden torque rise when combustion starts up again following deceleration fuel shutoff, the ME-SFI [ME] control unit adjusts the ignition angles of the cylinders 1 ignition coil (T1/1) to cylinders 3 ignition coil for (T1/3)) briefly towards "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 of the catalytic converter.
| Electrical function schematic for deceleration fuel shutoff | PE07.10-P-2714-97BBA | ||
| Overview of system components motor electronics (ME-SFI) fuel injection and ignition system | GF07.61-P-9997KJ |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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