D07.10-0100-79
Block diagram |
N3/36 | ME-SFI [ME] control unit | CAN C | Drive train CAN | |
N73/8 | Electronic ignition lock (EZS) control unit | CAN D | Diagnostic CAN | |
N127 | Drivetrain control unit | Flex E | Chassis FlexRay | |
N118/9 | Fuel pump control unit | S | Default | |
X11/4 | Diagnostic connector | O | Optional |
D47.40-0002-79
Vehicle overview |
N118/9 | Fuel pump control unit |
Location
The fuel pump control unit (N118/9) is located under the driver's seat.
Task
The fuel pump control unit (N118/9) regulates the fuel pump with fill level sensor (M3/6) in accordance with the requirements and sends information about the current fuel pressure to the ME-SFI control unit (N3/36).
To do this, the fuel pump control unit (N118/9) fulfills the following tasks:
Reading in of signals
Evaluation of signals
Output of signals and actuation of components
Regulation of the fuel pump with fill level sensor (M3/6)
Fill level evaluation of the fuel tank
Emptying the fuel tank
Diagnosis
Reading in of signals
Signals are read in via the following connections:
Direct lines
Drive train CAN (CAN C)
Direct lines
Terminal 15
Chassis 30
"Fuel pump with fill level sensor (M3/6) signal ON" from ME-SFI control unit (N3/36)
Fuel fill level and fuel pressure from the fuel pump with fill level sensor (M3/6)
Drive train CAN (CAN C)
Fuel pump with fill level sensor (M3/6) ON
Fuel specified pressure
Evaluation of signals
The read in signals are evaluated by the integral microprocessor, and the relevant assembly parts are actuated.
Output of signals and actuation of components
Signals are read in via the following connections:
Direct lines
Drive train CAN (CAN C)
Direct lines
Power supply of the fuel pressure sensor (5 V) integrated in the fuel pump with fill level sensor (M3/6)
Fuel pump ground connection with fill level sensor (M3/6)
Fuel pump fill level sensor AC voltage signal (M3/6) (Phase U)
Fuel pump with fill level sensor AC voltage signal (M3/6) (Phase V)
Fuel pump with fill level sensor AC voltage signal (M3/6) (Phase W)
Drive train CAN (CAN C)
Fuel pressure
Fuel-tank level
Diagnostic data
Regulation of the fuel pump with fill level sensor (M3/6)
Switching on the fuel pump with fill level sensor (M3/6) takes place if the respective signal is received by the fuel pump control unit (N118/9). This signal is transmitted redundantly by the ME-SFI control unit (N3/36) as a CAN signal via the drive CAN (CAN C) and switched directly as a ground signal. The fuel pump control unit (N118/9) detects the current fuel pressure via a signal from fuel pressure sensors integrated in the fuel pump with fill level sensor (M3/6) and sends this information to the ME-SFI control unit (N3/36) via the drive CAN (CAN C). To control the fuel pump with fill level sensor (M3/6), the ME-SFI control unit (N3/36) evaluates the fuel pressure and the engine load request and sends the "fuel specified pressure" CAN signal to the fuel pump control unit (N118/9). This evaluates the CAN signal and actuates the fuel pump with fill level sensor (M3/6) with a three phase shifted alternating current in such a way that the actual fuel pressure corresponds to the specified value. The fuel pressure is regulated dependent on the fuel temperature and the engine speed from approximately 4.5 to 6.7 bar.
Fuel pump control unit limp-home mode (N118/9):
If the "fuel specified pressure" signal and the signal of the fuel pressure sensor integrated in the fuel pump with fill level sensor (M3/6) are missing, the fuel pump with fill level sensor (M3/6) is regulated as per a specified pressure value stored in the fuel pump control unit (N118/9)
If the CAN signal "fuel pump with fill level sensor (M3/6) ON" and the ground signal "fuel pump with fill level sensor (M3/6) ON" are missing or the signal is implausible, the fuel pump with fill level sensor (M3/6) is switched off
If the "circuit 15" CAN signal and the "circuit 15" direct signal are missing, the fuel pump control unit (N118/9), and therefore also the fuel pump with fill level sensor (M3/6), are switched off
Fill level evaluation of the fuel tank
The fuel pump control unit (N118/9) reads in the signal of the fill level sensor integrated in the fuel pump with fill level sensor (M3/6) for the fill level evaluation of the fuel tank.
The current fill level as a percentage and in liters is calculated from this signal and the nominal volume of the fuel tank and transmitted as a CAN signal to the ME-SFI control unit (N3/36). The fill level sensor is also checked for plausibility. In the event of implausible measurement values, a fault message is stored in the fault memory and a fill level of 0 % is sent to the ME-SFI control unit (N3/36).
Emptying the fuel tank
The fuel tank can be emptied via XENTRY Diagnostics and the fuel pump control unit (N118/9) without the engine running.
Diagnosis
The fuel pump control unit (N118/9) performs an own and component check.
Recognized errors are stored by the fuel pump control unit (N118/9) and sent via the drive CAN (CAN C) to the ME-SFI control unit (N3/36), powertrain control unit (N127) and, from there, they are sent via the suspension FlexRay (Flex E), electronic ignition lock (EZS) control unit (N73/8), and the diagnostics CAN (CAN D) to the diagnostics connection (X11/4).
Structure
The fuel pump control unit (N118/9) consists of a plastic housing with two connector couplings and the inner measuring and control electronics.
Voltage supply
The power supply takes place via circuit 30 and circuit 15 from the vehicle interior fuse and relay module (F152).
Ground connection
The ground connection takes place via driver seat base ground point 3 (W105/3).
Variants
The vehicle and engine variants are already stored in the fuel pump control unit (N118/9). After exchanging the fuel pump control unit (N118/9), a variant coding must be carried out.