Alternator Interface Function - GF07.10-P-1009MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Function requirements, general
- Engine runs
The ME-SFI [ME] control unit (N3/10) detects the engine running by evaluating the signals of the crankshaft Hall sensor (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
Alternator interface
The alternator interface makes it possible for the ME-SFI [ME] control unit to communicate with the alternator (G2) via the drive train LIN (LINC1). The control response of the alternator is controlled via the alternator interface. The maximum data rate between the ME-SFI control unit and the LIN control for the alternator is 19.2 kbit/s. The LIN control is not fitted with any direct outlets.
The ME-SFI [ME] control unit controls the alternator control response in order to reduce the charging voltage for an adequately charged on-board electrical system battery (G1) when the engine is in neutral, for example. This reduces both the engine load and the exhaust emissions.
The ME-SFI [ME] control unit evaluates the following variables for controlling the alternator:
- Engine speed
The crankshaft Hall sensor detects the engine RPM. The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
- On-board electrical system voltage
The front SAM control unit (N10/6) transmits the status of the on-board electrical system via the interior CAN (CAN B), the electronic ignition lock control unit (N73), the chassis FlexRay (Flex E), the powertrain control unit (N127) and the drive train CAN (CAN C1) to the ME-SFI [ME] control unit.
- Alternator utilization
The ME-SFI [ME] control unit controls the following functions:
- Alternator regulation depending on the on-board electrical system voltage and the engine requests
- Alternator overheating protection
- Fault management
The ME-SFI [ME] control unit transmits requests for displaying text and warning messages via the engine CAN (CAN C), the powertrain control unit, the chassis FlexRay, the electronic ignition lock control unit and the user interface CAN (CAN HMI) to the instrument cluster (A1).
The alternator performs continuous self-diagnosis and transmits the results via the drive train LIN to the ME-SFI [ME] control unit. This compares the results with other signals (for example, engine RPM, on-board electrical system voltage, time since engine start) and thus detects any alternator faults.
The following faults are identified:
- Line for the alternator interface (drive train LIN) has an open circuit or the interface driver in the ME-SFI [ME] control unit is defective (the alternator regulates in this case at 14.3 V)
- Electrical and mechanical fault at the alternator:
- Control or diodes defective
- Stator interruption or short circuit
- Excitation interruption
- Charging voltage and current not achieved
- Charging voltage too high
- A cracked or loose poly-V belt
A battery tester must be used to place a load on the on-board electrical system battery in order to check the charging voltage, since the charging voltage can be significantly reduced when the on-board electrical system battery is fully charged and under no load.
Circuit 61 signal:
Using information received by the ME-SFI [ME] control unit via the alternator interface, the circuit 61 signal is simulated and issued via the engine CAN to various control units (e.g. to the instrument cluster).
| Electrical function schematic for alternator interface | Engine 177.9 in model 205, 253 | PE07.10-P-2709-97FBD | |
| Engine 177.9 in model 213 up to model year 2021 | PE07.10-P-2709-97DBG | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 177.9 in model 205, 253 | GF07.70-P-9998MNA | |
| Engine 177.9 in model 213 up to model year 2021 | GF07.70-P-9998MNE |