Phantom view of fuel tank |
45 | Filler neck |
75 | Fuel tank |
75/2 | Aeration and ventilation valve |
M3 | Fuel pump (FP) |
N118 | Fuel pump control unit |
P47.10-2811-76
Location
The FSCU is installed on the right on the fuel tank.
Tasks
The fuel system control unit is supplied by the company "Continental Automotive GmbH" and has the in-house designation FSCM GEN4 (Fuel System Control Module Generation 4).
The fuel system control unit regulates the fuel pump 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
Direct input signals
Terminal 15
Terminal 30
Circuit 31
Signal "Fuel pump ON"
Left fuel tank fuel fill level sensor fuel level indicator (B4/1)
Right fuel tank fuel level indicator fill level sensor (B4/2)
Direct output signals
Ground connection for left fuel tank fuel level indicator fill level sensor
Fuel tank fuel level indicator fill level sensor ground connection, right
AC voltage signal for fuel pump (Phase U)
AC voltage signal for fuel pump (Phase V)
AC voltage signal for fuel pump (Phase W)
CAN input signals
Fuel pump ON
Fuel specified pressure
CAN output signals
Fuel pressure
Diagnostic data
Structure
The fuel system control unit consists of a fuel housing with two plug connections and internal measuring and control electronics.
Function
The function description is subdivided into the following points:
Controlling the fuel pump
Fuel system control unit limp-home mode
Fill level evaluation of fuel tank
Diagnosis
Tank drainage service
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. 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 depending on the fuel temperature and engine speed between approx. 4.5 and max. 6.7 bar.
Fuel system control unit limp-home mode
If the "fuel pump ON" ground signal is missing or is implausible, the fuel pump is switched off.
If the "specified fuel pressure" signal is missing or is implausible, the fuel pump is switched off.
If the "Circuit 15" signal is missing or implausible, the fuel system control unit and thus also the fuel pump is switched off.
Fill level evaluation of fuel tank
The FSCU reads in signals from the fuel tank fuel level indicator fill level sensor on the left and right 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 values of 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:
Parameter 01 for "fuel pump ON"
Time "0-99.999" s
Fuel specified pressure 5.5 bar
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 fuel system control unit is Star2-capable.