Component Description For Fuel Pump Control Unit - GF47.40-P-2001MRD
Engine 256.9 in model 213, 238
up to model year 2021
Engine 264.9 in model 213, 238, 257
up to model year 2021
Engine 274.9, 276.8 in model 213, 238
up to model year 2021
Models 213, 257, shown on model 213
Location
The fuel system control unit is mounted on the right beneath the bench in the rear.
Model 238
Location
The fuel system control unit is mounted on the right behind the trim on the side wall in the rear.
Task
The fuel system control unit regulates the fuel pump's (M3) delivery rate. To do this, the fuel system control unit evaluates various input signals.
Input signals via direct lines
The fuel system control unit reads in the following signals via direct lines:
- Signal "Fuel pump 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, sensor signal (B47)
Input signals via CAN
Amongst others, the fuel system control unit receives the following signals via the drive CAN (CAN C1):
- Terminal status of terminal 15
- Fuel system ON
- Fuel specified pressure
- Engine running status
- Engine torque
- On-board electrical system status
- Accelerator pedal position
The fuel system control unit evaluates all relevant input signals and actuates the fuel pump with three phase-offset alternating voltage signals:
- Alternating voltage phase U
- Alternating voltage phase V
- Alternating voltage phase W
Output signals via CAN
Amongst others, the fuel system control unit also transmits the following signals via the drive CAN:
- Fuel pressure
- Fuel pump status
- Fuel tank fill level
- Status of fuel system
- Diagnostic data
Variant coding must be performed after exchanging the fuel system control unit.
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 [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 control unit. To control the fuel pump, the ME-SFI [ME] control unit evaluates the fuel pressure and the load requirement. The requested fuel pressure is adjusted via an integrated controller by actuating the fuel pump. The low fuel pressure is controlled to between approx. 4 to a maximum of 6.7 bar, depending on the fuel temperature and the engine speed.
Limp-home mode
Limp-home functions for drive CAN and fuel pressure sensor failure are stored in the fuel system control unit:
- Upon failure of the drive train CAN the signals "fuel pump ON" and "terminal 15" are redundantly sent over a direct line from the ME-SFI [ME] control unit to the FSCU. The fuel pump regulates the pressure to a substitute value stored in the FSCU.
- For failure of the fuel pressure sensor the fuel pump is actuated over fail safe characteristics curve in the FSCU.
- If both the drive CAN and the fuel pressure sensor fail, the fuel pump is actuated with a voltage stored in the fuel system control unit.
Fuel tank fill level
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 which is dependent on the fuel tank volume. The FSCU therefore calculates the contents of the fuel tank and checks this for plausibility with the current fuel consumption of the engine.
The values checked for plausibility are transmitted via the CAN network in liters and percentage to the IC (A1). Upon reaching the reserve quantity a signal is sent to the IC which then issues a warning message.
Tank drainage service
The fuel tank can be emptied over the FSCU without the engine running.
To do this, the tank draining service must be called up with the diagnostic tester, and the following parameters must be entered:
- Parameter 01 for "fuel pump ON"
- Time 0 to 99.999 s
- Fuel specified pressure 5.5 bar
During emptying the ignition must remain switched on.
| Wiring diagram for FSCU | Engine 274.9, 276.8 in model 213 up to model year 2017 | PE47.40-P-2101-97DBA | |
| Engine 256.9, 264.9, 274.9, 276.8 in model 213 as of model year 2017 up to model year 2021 | PE47.40-P-2101-97DBC | ||
| Engine 256.9, 264.9, 274.9, 276.8 in model 238 up to model year 2021 | PE47.40-P-2101-97DCA | ||
| Engine 264.9 in model 257 up to model year 2021 | PE47.40-P-2101-97XBA |