Component description for fuel pump control unit - GF47.40-P-2001MI

ENGINE 272.9 (except 272.982) in MODEL 204.0/2 as of model year 2009 

ENGINE 272.9 (except 272.983) in MODEL 212 

ENGINE 272.9 (except 272.984) in MODEL 207 

ENGINE 272.9 in MODEL 204.9 

ENGINE 273.9 in MODEL 207, 212 

View of right rear compartment door sill, model 204 

Fig 1: Fuel System Control Unit - Shown On Model 204

Courtesy of MERCEDES-BENZ USA

Location 

The fuel system control unit is located under the trim of the right rear door sill.

View of the rear compartment without rear bench seat, model 207 

Fig 2: Fuel System Control Unit - Shown On Model 207

Courtesy of MERCEDES-BENZ USA

Location 

The fuel system control unit is located in the middle under the rear bench seat.

View of right rear compartment door sill, model 212 

Fig 3: Fuel System Control Unit - Shown On Model 212

Courtesy of MERCEDES-BENZ USA

Location 

The fuel system control unit is located under the trim of the right rear door sill.

Task 

The fuel system control unit is delivered by the company "Siemens VDO Automotive AG" and carries the internal designation FSCM-light(F  uel S  ystem C  ontrol M  odule light).

The fuel system 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).

Input and output signals 

The following input signals are evaluated by the fuel system control unit and appropriate output signals are emitted:

• Direct input signals 
• Direct output signals 
• CAN signals from fuel system control unit 
• CAN signals to fuel system control unit 

Direct input signals 

• Circuit 15
• Circuit 30
• Circuit 31
• "Fuel pump ON" ground signal
• Fuel pressure sensor, sensor signal (B4/7)

Direct output signals 

• Power supply for fuel pressure sensor (5 V)
• Fuel pressure sensor ground
• Fuel pump (12 V) (pulse width modulated signal (PWM signal)) (positive)
• Fuel pump (PWM signal) (minus)

CAN signals from fuel system control unit 

• Fuel pressure
• Diagnostic data

CAN signals to fuel system control unit 

• Fuel pump ON
• Specified fuel pressure

Body 

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 redundantly 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 system control unit also receives the CAN signal "nominal pressure of the fuel" from the ME-SFI [ME] control unit.

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.

The fuel system control unit evaluates the current fuel pressure, compares it with the specified fuel pressure and actuates the fuel pump by means of a PWM signal in such a way that the actual value corresponds to the specified value.

The fuel delivery volume is regulated variably from 0 to 130 l/h for a fuel pressure of 3.8 bar according to the fuel requirements.

Fuel system limp-home mode control unit 

• If the signal "Specified fuel pressure" is missing, a substitute value is created by the fuel system control unit and the fuel pump is appropriately actuated.
• If the signal "nominal pressure of the fuel" 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 provided if the internal controller fails (e.g. processor failure).

Diagnosis 

The fuel system control unit conducts an own and component check. If an error is detected, it is stored by the fuel system control unit and made available to the ME-SFI [ME] control unit via the drive train CAN and also an attached Diagnosis Assistance System (DAS) via the diagnostic CAN (CAN-D).

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 the DAS, and the following parameters are entered:

• Parameter 01 for "Fuel pump ON"
• Time "0-99999" seconds
• Specified fuel pressure 3.8 bar

During emptying the DAS must be connected and the ignition must remain 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.