Component Description For Fuel Pump Control Unit - GF47.40-P-2001MNH
Engine 176.9, 177.9 in model 463
as of model year 2019
Vehicle view of model 463.2
Location
The fuel system control unit is installed behind the trunk floor paneling.
Tasks
The fuel system control unit bears the internal designation FSCM-GEN 4 (F uel S ystem C ontrol M odule G eneration 4 ).
The fuel system control unit regulates the fuel pump (M3) according to demand and transmits information about the current fuel pressure and the fill level of the fuel tank to the ME-SFI control unit (N3/10). The following input signals are evaluated by the FSCU and the respective output signal is issued:
- Direct input signals
- Direct output signals
- CAN input signals via drive CAN (CAN C1)
- CAN output signals via drive CAN
Direct input signals
- Terminal 15
- Terminal 30
- Ground signal (fuel pump ON)
- Signal for fill level sensor for fuel tank fuel level indicator, left (B4/1) and fill level sensor for fuel tank fuel level indicator, right (B4/2)
- Low pressure fuel pressure sensor signal (B4/7)
Direct output signals
- Low pressure fuel pressure sensor power supply (5 V)
- Fuel tank fill level sensor fuel level indicator ground connection
- Low pressure fuel pressure sensor ground connection
- Actuation of the fuel pump (Phase U)
- Actuation of the fuel pump (Phase V)
- Actuation of the fuel pump (Phase W)
CAN input signals via drive CAN
- Fuel pump ON
- Fuel specified pressure
- Status of engine
- Engine torque
CAN output signals via drive CAN
- Fuel pressure
- Fuel tank fill level
- Status of fuel system
- Diagnostic data
Structure
The FSCU consists of a plastic housing with two connectors and the inner measuring and control electronics.
Function
The FSCU takes on the following functions:
- 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 a "fuel pump ON" signal is received by the FSCU. This signal is transmitted redundantly by the ME-SFI control unit as a CAN signal via the drive 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 CAN to the ME-SFI control unit.
To control the fuel pump, the ME-SFI control unit evaluates the fuel pressure and load requirement and sends the pulse width modulated signal (fuel specified pressure) 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 value of the fuel pressure corresponds to the specified value. The fuel pump pressure is regulated dependent on the fuel temperature and engine rpm to between approx. 4.5 up to a maximum of 6.7 bar.
Fuel system control unit limp-home mode
Limp-home functions for failure of the drive CAN and the low pressure fuel pressure sensor are stored in the FSCU:
- Upon failure of the drive CAN the signals "fuel pump ON" and "circuit 15" are redundantly sent over a direct line from the ME-SFI control unit to the FSCU. The fuel pump regulates the fuel pressure to a substitute value stored in the FSCU.
- Upon failure of the fuel pressure sensor the fuel pump is actuated over a pressure/rpm characteristics map stored in the FSCU.
- If both the drive CAN and the low pressure fuel pressure sensor fail, the fuel pump is controlled according to an rpm stored in the fuel system control unit.
Diagnosis
The FSCU performs a self and component diagnosis. Detected faults are stored by the fuel system control unit and made available to the ME-SFI control unit via the drive CAN and additionally via the diagnostic CAN (CAN D) to attached diagnostic equipment. The self and component diagnosis checks all inputs and outputs for short circuits, an on-board electrical system voltage as well as an open circuit. All signals from the sensors are also checked for plausibility. The respective limp-home functions are activated for known faults.
Tank drainage service
The fuel tank can be emptied over the FSCU 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" s
- Fuel specified pressure 5.5 bar
During draining, Xentry Diagnostics must remain connected and the ignition must remain switched on.
Variants
For adaptation to different vehicle, engine, fuel tank variants and fuel pumps, different parameter sets are stored in the FSCU. For in-service date and exchange of the FSCU the respective parameters must be selected over the variant coding.
| Wiring diagram for FSCU | PE47.40-P-2101-97ZHA |