Component description for fuel system control unit - GF47.40-P-2001MG
ENGINES 271.820 in MODEL 204.0/2/3
ENGINES 271.860 in MODEL 204.0/2/3, 207.3/4, 212.0/2
View of right rear compartment door sill, model 204
Location
For model 204.0/2 the fuel pump control unit is located below the paneling on the right rear door sill.
View of the rear compartment without rear bench seat, model 207
Location
For model 204.3 and model 207 the FSCU is located in the middle under the rear bench seat.
View of right rear compartment door sill, model 212
Location
The fuel system control unit is located under the trim of the right rear door sill.
Task
The fuel pump control unit is designated internally as FSCM light (Fuel System Control Module light).
The fuel pump control unit regulates the fuel pump (M3) according to need and transmits information via the current fuel pressure to the ME-SFI [ME] control unit (N3/10).
Direct input signals
- Circuit 15
- Circuit 30
- Circuit 31
- Ground signal "fuel pump ON"
- Fuel pressure sensor, sensor signal (B4/7)
Input and output signals
The following input signals are evaluated by the fuel pump control unit and appropriate output signals are emitted:
- Direct input signals
- Direct output signals
- CAN signals from fuel pump control unit
- CAN signals to fuel pump control unit
Direct output signals
- Power supply for fuel pressure sensor (5 V)
- Fuel pressure sensor mass
- Fuel pump + (12 V) (pulse width modulated signal (PWM signal)) (Plus)
- Fuel pump (PWM signal) (Minus)
CAN signals from fuel pump control unit
- Fuel pressure
- Diagnostic data
CAN signals to fuel pump control unit
- Fuel pump ON
- Fuel requirements
Design
The fuel system control unit consists of a fuel housing with two plugs and internal measuring and control electronics.
Function
The function description is subdivided into 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 a signal "fuel pump ON" is received by the fuel system control unit. This signal is sent redundant from the ME-SFI [ME] control unit as a CAN signal via the drive train CAN (CAN C) and as a ground signal.
The fuel pump control unit also receives the CAN signal "fuel requirements" from the ME-SFI [ME] control unit.
The fuel pump 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.
The fuel pump control unit evaluates the fuel pressure and the fuel requirements specification and actuates the fuel pump accordingly using a pulse width modulation signal.
The fuel delivery volume is regulated variably from 0 to 130 l/h for a fuel pressure of about 3.8 bar according to the fuel requirements.
Fuel system control unit limp-home mode
- If the signal "fuel requirements" is missing a substitute value is created and the fuel pump is appropriately actuated by the fuel system control unit.
- If the signal "fuel requirements" and the signal from fuel pressure sensor is missing, the fuel pump is actuated by an established permanent pulse width modulation signal (maximum delivery = 130 l/h).
- If both signals "Fuel pump ON" are missing, the fuel pump is actuated upon recognition of circuit 15.
- Various limp-home functions ensure that the fuel supply is also ensured for a failure of the internal control system (e.g. failure of the processor).
Diagnosis
The fuel system control unit conducts a self-test and a component test. Recognized errors are stored by the fuel pump control unit and sent to the Xentry diagnostics via the diagnostic CAN to the ME-SFI control unit via the drive train CAN.
Tank-draining function
The fuel tank can be emptied over the fuel system control unit 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 "0-99999" seconds
- Duty cycle of the PWM signal to 100%
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.