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

Engine 274 in model 447, 448 

except code XM0 (Facelift) 

Function requirements for the alternator interface, general points 

• Circuit 87M ON (Engine management ON)
• Engine runs

Alternator interface, general points 

G2Using the alternator interface, messages are exchanged via the drivetrain LIN (LIN C3) between the alternator () and the ME-SFI [ME] control unit (N3/34) and the control response of the alternator (G2) is controlled. To do this the ME-SFI [ME] control unit (N3/34) reads in the following signals:

• Signal acquisition and actuation module (SAM) control unit (N10/1), charge voltage specification via interior CAN (CAN B), electronic ignition lock control unit (EZS) (N73) and chassis CAN (CAN E)
• Crankshaft Hall sensor (B70/2), engine rpm over direct line

Function sequence for alternator interface 

G1The ME-SFI [ME] control unit (G2/34) regulates the alternator control response (N3), for example in order to reduce the regulation voltage (charging voltage) when the on-board electrical system battery () is sufficiently charged.

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

The ME-SFI [ME] control unit (N3/34) controls the following functions with the aid of specifications issued by the signal detection and actuation module (SAM) control unit (N10/1):

• Control of the alternator (G2) according to specifications issued by the signal detection and actuation module (SAM) control unit (N10/1) or for engine requirements according to specifications in the ME-SFI [ME] control unit (N3/34)
• Delayed adaptation of the charging voltage in the event of frequent load changes at the alternator (G2) when in idle to stabilize the idling speed
• Recognized faults via the chassis CAN (CAN E) to the IC control unit (IC) (A1/1), for actuation of the respective symbols and display messages
• Charging of the on-board electrical system battery (G1) increases in the deceleration phases (fuel savings)
• Generate a circuit 61 signal (alternator (G2) in function)

The alternator (G2) performs continuous self-diagnosis and transmits the results when requested to the ME-SFI [ME] control unit (N334). This compares the results with other signals (such as the engine rpm, on-board electrical system voltage, time since engine start) and thus detects any alternator faults (G2).

The following faults are identified:

• Short circuit or open circuit at output "circuit -61 signal" from ME-SFI [ME] control unit (N3/34)
• Line of the alternator interface (drivetrain LIN (LIN C3)) interrupted or interface driver in the ME-SFI [ME] control unit (N3/34) defective (the alternator (G2) regulates in this case at 14.3 V)
• Electrical and mechanical fault on the alternator (G2):
  • Control or diodes defective
  • Stator interruption or short circuit
  • Excitation interruption
  • The charging voltage and charging current are not reached
  • Charging voltage too high
  • A cracked or loose poly-V belt

Diagnosis

To check the charging voltage, the on-board electrical system battery (G1) must be loaded with a battery tester since the charging voltage can be significantly reduced when the on-board electrical system battery (G1) is fully charged and under no load.

"Circuit -61 signal"

For alternators (G2) with an alternator interface the "circuit -61-signal" line is not needed. From the information which the ME-SFI [ME] control unit (N3/34) receives via the alternator interface, the "circuit-61 signal" simulated in the MESFI [ME] control unit (N3/34) and issued via the CAN network (e.g. to the IC control unit (KI) (A1/1)).

	Electrical function schematic for alternator interface	Engine 274 in model 448 except code XM0 (Facelift)	PE07.10-S-2709-97VDC
		Engine 274 in model 447 except code XM0 (Facelift)	PE07.10-S-2709-97TRC
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-S-9998TRC