Shown on model 205.0 |
N118 | Fuel system control unit |
P47.40-2119-76
Location
The fuel system control unit is located under the trim of the right rear rocker panel.
Task
The fuel system control unit is supplied by the "Continental Automotive GmbH" company and bears the internal designation FSCM (GEN4Fuel 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
Direct input signals
Terminal 15
Terminal 30
Circuit 31
Signal "Fuel pump ON"
Left fuel tank fuel level indicator fill level sensor (B4/1)
Right fuel tank fuel level indicator fill level sensor (B4/2)
Fuel pressure sensor sensor signal (B4/7)
Direct output signals
Fuel pressure sensor power supply (5 V)
AC voltage signal for fuel pump (Phase U)
AC voltage signal for fuel pump (Phase V)
AC voltage signal for fuel pump (Phase W)
Fuel pump (FP)
CAN input signals
Fuel pump ON
Fuel specified pressure
CAN output signals
Fuel pressure
Diagnostic data
Body
The fuel system control unit comprises a plastic housing with two electrical connections.
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
Variants
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 fuel pressure corresponds to the specified value. The fuel pump pressure is controlled dependent on the fuel temperature and the engine rpm between about 4.5 to a maximum of 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 is implausible, the fuel system control unit and therefore also the fuel pump are switched off.
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 volumes of the fuel tank, the current fill level in percent and the reserve quantity are calculated from the values measured in ohms and transmitted to the CDI control unit with an appropriate 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:
Parameter 01 for "fuel pump ON"
Time "0-99999" seconds
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 FSCU is diagnosis-capable (Star2).