Alternator Interface Function - GF07.10-S-1009TRJ

Engine 274 in model 447.6/7 

with code XM0 (Facelift) 

Function requirements for the alternator interface, general points 

• Circuit 87M ON (Engine management ON)
• Engine running.

Alternator interface, general points 

Via the alternator interface, messages are exchanged via the drive LIN (LIN C1) between the alternator (G2) and the ME-SFI [ME] control unit (N3/34) and the control response of the alternator is controlled. To do this the ME-SFI [ME] control unit reads in the following signals:

• Signal acquisition and actuation module (SAM) control unit (N10/1), target charging voltage
• Crankshaft Hall sensor (B70/2), engine rpm

Function sequence for alternator interface 

The ME-SFI [ME] control unit controls the control response of the alternator to, for example, reduce the charging voltage in the case of a sufficiently charged onboard electrical system battery (G1).

The engine load reduced in this way causes the fuel consumption to be reduced.

The ME-SFI [ME] control unit controls the following functions using the inputs of the signal acquisition and actuation module control unit (SAM):

• Regulation of alternator according to the inputs of the signal acquisition and actuation module control unit (SAM) or in the case of engine-related requests according to the inputs in the ME-SFI [ME] control unit
• Adapting the charging voltage with a delay in the event of frequent load changes at the alternator in idle to stabilize the idling speed.
• Communication of detected faults to the instrument cluster control unit (IC) (A1/1) for the actuation of the corresponding symbols and display messages.
• Increased charging of on-board electrical system battery in overrun mode (fuel saving)
• Generate signal "circuit 61" (alternator in operation).

The alternator performs continuous self-diagnosis and transmits the results when requested to the ME-SFI [ME] control unit. This compares the results with additional signals (e.g. engine speed, on-board electrical system voltage, time after engine start) and detects alternator faults from this.

The following faults are identified:

• Short circuit or open circuit at output of "circuit 61" signal from the ME-SFI [ME] control unit
• Line of alternator interface (drive LIN (LIN C1)) interrupted or interface driver in ME-SFI [ME] control unit defective (alternator regulates in this case to 14.3 V)
• Electrical and mechanical fault at the alternator:
  • Control or diodes defective
  • Stator interruption or short circuit
  • Excitation interruption
  • Charging voltage and charging current not achieved.
  • Charging voltage too high
  • A cracked or loose poly-V-belt

Diagnosis

To check the charging voltage, the on-board electrical system battery must be loaded with a battery tester since the charging voltage can be significantly reduced when the on-board electrical system battery is fully charged and under no load.

Signal "circuit 61"

For alternators with alternator interface, the signal line "circuit 61" has been omitted. From the information that the ME-SFI [ME] control unit receives via the alternator interface, the "circuit 61" signal is simulated in the ME-SFI [ME] control unit and output via the CAN network (e.g. to the instrument cluster control unit (IC) (A1/1)).

	Function schematic for alternator interface		PE07.10-S-2504-97TRM
	Electrical function schematic for alternator management		PE54.10-S-2064-97TRL
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-S-9998TRJ