(Component Description For Fuel Pump Control Unit - GF47.40-P-2001MMR)
ENGINE 157.9 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.
Tasks
The FSCU carries the internal designation UFPC AMG (U niversal F uel P ump C ontroller for AMG).
The FSCU controls the fuel pump according to need (M3) and transmits information about the current fuel pressure to the ME-SFI [ME] control unit (N3/10) via the drive train CAN (CAN C).
Input and output signals
The following input signals are evaluated by the FSCU and the respective output signal is issued:
- CAN input signals
- CAN output signals
- Direct input signals
- Direct output signals
CAN input signals
- Fuel pump ON
- Data for variant coding
CAN output signals
- Fuel supply status
- Diagnostic data
Direct input signals
- Terminal 15
- Terminal 30
- Circuit 31
- Ground signal "Fuel pump ON"
- Fuel pressure sensor sensor signal (B4/7)
- Pulse width modulated signal "fuel specified pressure"
Direct output signals
- Fuel pressure sensor power supply (5 V)
- Fuel pressure sensor ground connection
- AC signal for fuel pump (phase A)
- AC signal for fuel pump (phase B)
- AC signal for fuel pump (phase C)
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 in the following points:
- Controlling the fuel pump
- Fuel system control unit limp-home mode
- Diagnosis
- Tank drainage service
Controlling the fuel pump
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 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-SFI [ME] control unit. To control the fuel pump, the ME-SFI [ME] control unit evaluates the fuel pressure and load requirement and sends the "specified fuel pressure" pulse width modulated signal to the fuel system control unit. This evaluates the PWM signal and actuates the fuel pump with three phase-shifted alternating current as required, so that the actual fuel pressure corresponds to the specified value.
The fuel pump pressure is controlled dependent on the fuel temperature and the engine rpm between about 4.5 to a maximum of 6.7 bar.
Fuel system control unit limp-home mode
- If the "fuel pump ON" ground signal fails or is implausible, the fuel pump is shut off.
- If the "fuel specified pressure" signal fails or is implausible, the fuel pumps are shut off.
- If the "Circuit 15" signal fails or is implausible, the fuel system control unit (and therefore the fuel pump) is switched off.
Diagnosis
The FSCU performs am 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 drainage service
The fuel tank can be emptied over the FSCU without the engine running.
To do this, the tank 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 FSCU. After replacement of the FSCU a variant coding must be carried out.
| Wiring diagram for FSCU | N118 | PE47.40-P-2101-97NAA |