Component description for fuel pump control unit

P47.40-2058-11

View of the rear seat area door sill on the right, model 204

N118 Fuel pump control unit

Location

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

P47.40-2075-11

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

N118 Fuel pump control unit

Location

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

P47.40-2062-11

View of the rear seat area door sill on the right, model 212.0

N118 Fuel pump control unit

Location

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

Task

The fuel pump control unit is supplied by "VDO Automotive AG" and carries the internal designation 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).

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 input signals

 CAN output signals

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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 mass

- Fuel pump + (12
V) (pulse width modulated signal (PWM signal)) (Plus)

- Fuel pump (PWM signal) (Minus)

CAN input signals

- Fuel pump ON

- Nominal pressure of the fuel

CAN output signals

- Fuel pressure

- Diagnostic data

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Design

The fuel pump control unit consists of a fuel housing with two plugs and internal measuring and control electronics.

Function

The function is described at the following points:

 Fuel pump regulation

 Fuel pump 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 pump 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.

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The fuel pump control unit also receives the CAN signal "nominal pressure of the fuel" 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 control unit.

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

Depending on the fuel requirements, fuel pressure is regulated variably between about 3.0 and 5.5 bar.

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Fuel pump limp-home mode control unit

- If the signal "nominal pressure of the fuel" is missing a substitute value is created and the fuel pump is appropriately actuated by the fuel pump control unit.

- 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 ensured for a failure of the internal control system (e.g. failure of the processor).

Diagnosis

The fuel pump control unit conducts an own and component check. If an error is detected, it is stored by the fuel pump 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 pump 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 5.5 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 pump control unit. After replacing the fuel pump control unit, variant coding must be conducted.