Alternator Control, Basic Function - GF15.40-P-1058A

Engine All (4xWD) 

Engine All (CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Alternator control function 
  • Alternator self-diagnosis 

General 

To optimally control the charging voltage of the alternator, the alternator and the combustion engine control unit exchange data via the alternator control function. The alternator control function makes the exchanged data plausible and corrects it depending on the vehicle's operating state. In addition, the alternator control function records mechanical or electrical faults in the alternator.

Function requirements 

• Engine management ON (circuit 87M)
• Engine in operation

Function 

Alternator control function 

The alternator control function requests the optimized charging voltage from the alternator. The optimized charging voltage is calculated from the following information:

• Specified voltage of the alternator management
• Corrections of output management. In order to calculate the optimized charging voltage for the alternator, the following processes take place:
  • Reading out the operating rate of the alternator:

    In order to control the power output of the alternator, the combustion engine control unit assesses the operating rate of the alternator. To this end, it uses the data transmitted by the alternator.

  • Calculating the specified voltage of the alternator:

    In order to determine the specified voltage of the alternator, the powertrain control unit uses the operating rate of the alternator. This involves the alternator control function.

  • Optimizing the specified voltage of the alternator. In order to record the on-board electrical system voltage, the following information is read in and compared:
    • The calculated specified voltage of the alternator
    • The actual value of the alternator voltage

In order to compensate for fluctuations in the on-board electrical system voltage in certain vehicle operating states, the output management optimizes the specified voltage, e.g. at engine start. This results in the optimized charging voltage.

Alternator self-diagnosis 

The alternator performs self-diagnosis continuously. On request, it provides its status as a signal.

The alternator control function detects the following electrical or mechanical faults:

• Line of the alternator control function has an open circuit
• Control or diodes defective
• Interruption or short circuit in the stator
• Excitation interruption
• Charging voltage too low or too high
• Cracked poly-V-belt
• Poly-V belt tension too low or too high

	Function schematics
	Function schematic for alternator interface	Engine 260, 282, 608 in model 118, 177, 247 Engine 264 in model 167	PE07.10-P-2504-97A
		Engine 176, 177 in model 167	PE07.10-P-2504-97B
		Engine 139 in model 118, 177, 247	PE07.10-P-2504-97C
		Engine 256 in model 213, 238 as of model year 2021 Engine 264 in model 213, 238, 257 as of model year 2021 Engine 654 in model 118, 167, 177, 247 Engine 654 in model 213, 238, 257 as of model year 2021 Engine 656 in model 167	PE07.10-P-2504-97D
		Engine 177 in model 192, 232 except code ME10 (Hybrid vehicle (plug-in, PHEV))	PE07.10-P-2504-97E
		Engine 254 in model 167 as of model year 2023 Engine 254 in model 206, 214, 236, 254	PE07.10-P-2504-97F
		Engine 279 in model 223	PE07.10-P-2504-97G
		Engine 656 in model 223	PE07.10-P-2504-97H
		Engine 656 in model 464	PE07.10-P-2504-97I
	Additional basic functions
	Combustion engine control unit, basic function		GF07.08-P-9890A