STSTEM Description

Battery sensor measures the voltage, current and the temperature of battery.
BCM judges battery condition according to the battery sensor signal.
BCM calculates the target power generation voltage according to battery condition and sends calculated value as alternator voltage request signal to ECM via CAN communication.
Signals are exchanged via LIN communication between alternator and ECM, and control response of alternator is controlled in this way. (Alternator interface function)
NOTE:
Function requirements for the alternator interface, general points:
- Engine management is ON
- Engine is running
ECM reads in the following signals for alternator control.
- Crankshaft position sensor (with rotational recognition) and engine speed
- Battery voltage
- Alternator status via LIN communication
ECM regulates the control response of alternator, for example in order to reduce the charging voltage when idling if battery is sufficiently charged.
This reduces the engine load, thus also reducing fuel consumption and improving exhaust emissions.
ECM controls the following functions.
- Switching on of alternator dependent on the condition of battery and the requirements from engine.
- Regulation of alternator according to characteristics maps stored in the ECM. To do this the charging voltage is determined by ECM.
- Adapting the charging voltage with a delay in the event of frequent load changes at alternator in idle to stabilize the idling speed.
- Protecting alternator against overheating.
- Generation of "alternator is operating" signal.
- Transmitting the detected malfunctions via CAN communication.
- Keeps charging voltage at a low value and charges battery more strongly in the deceleration phases (fuel saving).
Alternator performs continuous self-diagnosis and transmits the results when requested to ECM.
ECM compares the results with other signals (for example, engine speed, battery voltage, time since engine start) and thus detects following alternator malfunctions.
- Open circuit in alternator interface (LIN communication) line or interface driver in ECM malfunction.
  NOTE: Charge voltage of 14.3V is specified for this malfunction.
- Electrical and mechanical following malfunction at alternator.
  - IC regulator or diodes malfunction
  - Stator interruption or short circuit
  - Excitation interruption
  - Charging voltage and charging current are not reached
  - Charging voltage too high
  - Cracked or loose drive belt