Component description for fuel pump control unit - GF47.40-P-2001MMO
ENGINE 276.9 in MODEL 212.095
View of right door sill in the rear compartment
Location
The fuel system control unit is located under the trim of the right rear door sill.
Task
The fuel system control unit bears the internal designation FSCM-EC (F uel S ystem C ontrol M odule for E lectronically C ommutated fuel pumps).
The FSCU regulates the fuel pump (M3) as required and transmits information about the current fuel pressure, fuel grade and temperature via the drive train CAN (CAN C) 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
Direct input signals
- Circuit 15
- Circuit 30
- Circuit 31
- "Fuel pump ON" ground signal
- Sensor signal from fuel pressure sensor (B4/7)
- Sensor signal from fuel quality sensor (B4/31)
Direct output signals
- Power supply for fuel pressure sensor (5 V)
- Power supply for fuel quality sensor (5V)
- Fuel pressure sensor ground
- 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
- Specified fuel pressure
CAN output signals
- Fuel pressure
- Fuel grade/temperature
- Diagnostic data
Body
The fuel system 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 actuation
- Fuel system limp-home mode control unit
- Diagnosis
- Tank-draining function
Fuel pump actuation
Switching on of the fuel pump takes place if the signal "fuel pump ON" is received by the FSCU from the ME-SFI [ME] control unit. This signal is transmitted once redundantly directly as a ground signal and once via the drive train CAN.
The fuel pump control unit also receives the CAN signal "nominal pressure of the fuel" from the ME-SFI [ME] control unit via the drive CAN.
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 system control unit evaluates the current fuel pressure, compares it with the specified fuel pressure and actuates the fuel pump appropriately by means of these phase-offset AC voltage signals in such a way that the actual value corresponds to the specified value.
The fuel pump pressure is regulated dependent on the fuel temperature and the engine RPM between about 4.0 and a maximum of 6.7 bar.
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 from the fuel pressure sensor is missing the fuel pump is actuated over a consumption-dependent limp-home mode characteristic.
- If the signal "specified fuel pressure" and the signal from the fuel pressure sensor are missing, the fuel pump is actuated by an established replacement voltage.
Diagnosis
The fuel pump control unit conducts an own and component check. Recognized errors are stored by the fuel pump control unit and sent to the Xentry diagnostics via the diagnostic CAN to the ME-SFI control unit via the drive train CAN.
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 Xentry
Diagnostics, and the following parameters are entered:
- Time "0-99999" minutes
- Specified fuel pressure 5.0 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 fuel system control unit. After replacing the fuel system control unit, variant coding must be conducted.
| Designation | Unit | Values | Tolerance range | Remarks |
|---|---|---|---|---|
| Fuel system control unit (N118) | ||||
| Supply voltage | V | 13.5 | Terminal 30 | |
| Voltage limit: Minimum Maximum | V | 6.0 | ||
| V | 16.0 | |||
| Power consumption: No-load current (typical) | μA | 7 | at 13 V and 23°C | |
| No-load current (maximum) readiness-to-operate | μA | 300 | ||
| mA | 100 | |||
| mA | 300 | |||
| Reverse polarity protection | Through triggering a fuse | |||
| Short-circuit resistance | For power supply, load outputs and signal lines | |||
| Operating temperature range | °C | -40 - 85 | ||
| Diagnosis capability | Yes | |||
| Flash capability/coding capability | Yes/yes | |||
| Special features | De-tanking service (de-tanking without engine running) | |||
| Fuel pressure sensor (B4/7) | ||||
| Model | Capacitive, absolute measuring sensor | |||
| Supply voltage | V | 5.0 | ±0.25 V | |
| Signal voltage | V | 0.3 - 4.5 | Linear, signal proportional to fuel pressure | |
| Measuring range | bar | 0.5 - 10.0 | ||
| Operating temperature range | °C | -40 - 80 | ||
| Fuel quality sensor (B4/31) (for code (494) USA version) (for code (929) Engine for ethanol fuel) |
Permittivity measuring cell with a combined NTC resistor (negative temperature coefficient (NTC thermistor)) | |||
| Model | ||||
| Supply voltage | V | 9 - 18 | ||
| Power consumption | mA | <25 | ||
| Measuring range (ethanol contents) | % | 0 - 100 | ||
| Ambient temperature | °C | -40 - +125 | ||
| Fuel temperature | °C | -40 - +90 | ||
| Maximum fuel pressure | bar | 10 | ||
| Maximum flow rate | l/h | 400 | ||
| Fuel pump (M3) | ||||
| Model | Two-stage flow pump with a 3- phase AC motor | |||
| Supply voltage | V | 12.0 | 3 phase-shifted AC signals from FSCU | |
| Delivery rate maximum | l/h | 177 | With fuel pump (VDO G43) |
| Wiring diagram for fuel system control unit | N118 | PE47.40-P-2101-97DAD |