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Component Description For Fuel Pump Control Unit - GF47.40-P-2001OGF

Engine 642.8 in model 166 

as of model year 2016 

Engine 642.8 in model 292 

Fig 1: Fuel Pump Control Unit Components Location - Engine 642.8 In Model 166 As Of Model Year 2016
G14139039Courtesy of MERCEDES-BENZ USA

Shows model 166.0 

Location 

The fuel system control unit is installed behind the load compartment trim on the right on the wheel arch.

Task 

The fuel system control unit is supplied by the "Continental Automotive GmbH" company and bears the internal designation FSCMGEN4 (Fuel System Control Module Generation 4). The fuel system control unit regulates the fuel pump (M3) in accordance with requirements and transmits information about the current fuel pressure to the CDI control unit (N3/9).

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 

CAN output signals 

Structure 

The fuel system control unit consists of a plastic housing with two plug connections and an internal measuring and controller unit.

Function 

The function description is subdivided into the following points:

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 sent redundantly by the CDI control unit as a CAN signal via the drive train CAN (CAN C1) 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 CDI control unit. To control the fuel pump, the CDI control unit evaluates the fuel pressure and load requirement and sends the "specified fuel pressure" pulse width modulated signal 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 the engine rpm between about 4.5 and a maximum of 6.7 bar.

Fuel system control unit limp-home mode 

Fill level evaluation of fuel tank 

The FSCU reads in the fuel tank fuel level indicator fill level sensor to compute and evaluate the fill level of the fuel tank. The nominal volume of the fuel tank, the current fill level in percent and the reserve quantity are calculated from the values measured in ohms and sent to the CDI control unit together with a corresponding signal. Furthermore the fill level sensors are checked for plausibility. In the event of implausible measurements, a fault message is sent to the CDI control unit.

Diagnosis 

The FSCU performs am own and component check. Recognized errors are stored by the fuel system control unit and sent to Xentry Diagnostics via the diagnostic CAN to the CDI control unit via the drive train CAN.

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:

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 FSCU. After replacement of the FSCU a variant coding must be carried out. The FSCU is diagnosis-capable (Star2).

  Wiring diagram for FSCU   PE47.40-P-2101-97NBA 
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