(Component Description For Fuel Pump Control Unit - GF47.40-P-2001MMG)
ENGINE 276.8/9, 278.9 in MODEL 166
up to model year 2016
View of trunk from right
Location
The FSCU is located under the cover in the right trunk.
Task
The fuel system control unit bears the internal designation FSCM-EC (F uel S ystem C ontrol M odule for E lectronically C ommutated fuel pumps).
The fuel system control unit regulates the fuel pump (M3) as required and sends information about the current fuel pressure, fuel grade and temperature via the drive train CAN (CAN C) to the ME-SFI [ME] control unit (N3/10).
Input and output signals
The following input signals are evaluated by the fuel system control unit and appropriate output signals are emitted:
- Direct input signals
- Direct output signals
- CAN input signals
- CAN output signals
Direct input signals
- Terminal 15
- Terminal 30
- Circuit 31
- "Fuel pump ON" ground signal
- Fuel pressure sensor sensor signal (B4/7)
- Sensor signal for fuel quality sensor (B4/31) (for engine 276 with code 494 (USA version) and code 929 (Engine for ethanol fuel))
Direct output signals
- Fuel pressure sensor power supply (5 V)
- Fuel quality sensor power supply (5V) (with engine 276 with code (494) USA version and code (929) Engine for ethanol fuel)
- Fuel pressure sensor ground connection
- AC voltage signal for fuel pump (Phase U)
- AC voltage signal for fuel pump (Phase V)
- AC voltage signal for fuel pump (Phase W)
CAN input signals
- Fuel pump ON
- Fuel specified pressure
CAN output signals
- Fuel pressure
- Diagnostic data
Body
The fuel system control unit consists of a fuel housing with two plug connections and internal measuring and control electronics.
Function
The function is described at the following points:
- Fuel pump regulation
- Fuel system limp-home mode control unit
- Diagnosis
- Tank-draining function
Fuel pump regulation
Switching on of the fuel pump takes place if the signal "fuel pump ON" is received by the fuel system control unit. This signal is transmitted redundantly by the ME-SFI [ME] control unit as a CAN signal via the drive train CAN and directly as a ground signal.
The fuel system control unit also receives the CAN signal "nominal pressure of the fuel" from the ME-SFI [ME] control unit via the drive train CAN.
The fuel system control unit detects the current fuel pressure by means of a voltage signal from the fuel pressure sensor and transmits this information via the drive train CAN to the ME control unit.
The fuel system control unit evaluates the current fuel pressure, compares it with the specified fuel pressure and actuates the fuel pump appropriately by means of these phase-offset AC voltage signals in such a way that the actual value corresponds to the specified value. The fuel pump pressure is regulated dependent on the fuel temperature and the engine rpm between about 4.0 and a maximum of 6.7 bar.
Fuel system control unit limp-home mode
- If the signal "specified pressure of the fuel" is missing a substitute value is created and the fuel pump is appropriately actuated by the fuel system control unit.
- If the signal from the fuel pressure sensor is missing, a consumption-specific limp-home mode characteristic is used to actuate the fuel pump.
- If the "Specified fuel pressure" signal and the signal from the fuel pressure sensor are missing, the fuel pump is actuated with a defined substitute voltage.
Diagnosis
The fuel system control unit conducts an own and component check. Recognized faults are stored by the fuel system control unit and an attached diagnostic unit (XD) is made available via the drive train CAN to the ME-SFI [ME] control unit and additionally via the diagnostic CAN (CAN D).
Tank-draining function
The fuel tank can be emptied over the fuel system control unit without the engine running. To do this, the container draining function is selected using Xentry Diagnostics, and the following parameters are entered:
- Parameter 01 for "fuel pump ON"
- Time "0-99.999" seconds
- Fuel specified pressure 5.5 bar
During draining, Xentry Diagnostics must remain connected and the ignition must remain switched on.
Variants
The vehicle and engine variants are already stored in the fuel system control unit. After replacing the fuel system control unit, variant coding must be conducted.
| Wiring diagram for fuel system control unit | N118 | PE47.40-P-2101-97NAA |