Component Description For Fuel Pump Control Unit - GF47.40-P-2001MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Shown on right rear entrance (model 205.0)
Location
The fuel system control unit for model 205.0/2, 253 is located in the door sill next to the right rear seat. In model 205.3/4, the fuel system control unit is located beneath the right side paneling in the rear next to the right rear seat.
For model 213 the FSCU is located under the right rear seat.
Task
The fuel system control unit bears the internal designation FSCM-GEN 4 (F uel S ystem C ontrol M odule GEN eration 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).
Input and output signals
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 train CAN (CAN C1)
- CAN output signals via drive train CAN
Direct input signals
- Ground signal "fuel system ON"
- Sensor signal from fuel tank fuel level indicator fill level sensor, left (B4/1)
- Sensor signal from fuel tank fuel level indicator fill level sensor, right (B4/2)
- Fuel pressure sensor signal (B47)
Direct output signals
- 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 train CAN (example)
- Terminal status of terminal 15
- Fuel system ON
- Fuel specified pressure
- Status of engine
- Engine torque
- On-board electrical system status
- Accelerator pedal position
CAN output signals via drive train CAN (example)
- Fuel pressure
- Rpm of fuel system
- Diagnostic data
- Fuel tank fill level
- Status of fuel system
Controlling the fuel pump
The fuel system control unit actuates the fuel system as soon as it receives the "Fuel system ON" request from the ME-SFI [ME] control unit via drive train CAN or as a direct ground signal.
The fuel pressure is recorded by the fuel pressure sensor. The FSCU directly reads in the signals from the fuel pressure sensor and transmits this information about the fuel pressure to the ME-SFI [ME] control unit via the drive train CAN. The ME control unit evaluates the fuel pressure and load requirement. It then sends a pulse-width-modulated signal (target fuel pressure) to the fuel pump control unit via a direct line and redundantly via the drive CAN. The fuel system control unit actuates the fuel system accordingly with three phase-offset AC voltage signals.
The fuel system control unit controls the fuel system pressure depending on the fuel temperature and the engine rpm between 4.5 to 6.7 bar.
Fuel system control unit limp-home mode
Limp-home functions for failure of the drive train CAN and the fuel pressure sensor are stored in the FSCU.
- If the drive train CAN fails, the fuel system control unit merely evaluates the "Fuel system ON" request that is sent by the ME-SFI [ME] control unit via the direct line. The fuel system then sets the fuel system pressure to a stored substitute value.
- If the fuel pressure sensor fails, the fuel system is actuated over a pressure/rpm characteristics map stored in the FSCU.
- If both the drive train CAN and the fuel pressure sensor fail, the fuel pump according to an rpm stored in the FSCU.
Fill level evaluation of fuel tank
The FSCU determines the current resistance of the fuel level indicator fuel tank fill level sensor over a voltage measurement and therefore the fill level of the fuel.
The determined voltage value is compared with a characteristic stored in the FSCU. The FSCU calculates the contents of the fuel tank and checks this for plausibility with the current fuel consumption of the engine.
The fuel system control unit sends the plausibilized values in liters and percentage to the instrument cluster (A1). When the reserve quantity has been reached, the fuel system control unit sends a signal to the instrument cluster, which then issues a warning message.
Diagnosis
The FSCU performs a self and component diagnosis. Recognized faults are stored by the fuel system control unit and sent via the drive train CAN to the ME-SFI [ME] control unit and, if necessary, via the diagnostic CAN (CAN D) to a connected diagnostic unit.
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 sensor signals 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.
In order to do this, the tank draining service must be called up using the diagnostic unit and the following parameters entered:
- Parameter 01 for "fuel pump ON"
- Time "0-99.999" s
- Fuel specified pressure 5.5 bar
During emptying the diagnostic unit must be connected and the ignition must remain 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 | Engine 177.9 in model 205 up to model year 2019Engine 177.9 in model 253 | PE47.40-P-2101-97FBA | |
| Engine 177.9 in model 205 as of model year 2019 | PE47.40-P-2101-97FBB | ||
| Engine 177.9 in model 213 up to model year 2021 | PE47.40-P-2101-97DBA |