Automatic Transmission - 6-Speed PowerShift Transmission - MPS6/6DCT450 - Diagnostic Strategy

Alternator control (Smart Charge) ItemDescription 1PCM 2Consumers 3Alternator 4LIN (local interconnect network) databus Comments: Via the LIN databus, the PCM receives information about the alternator load, and the alternator receives information about the optimum voltage calculated by the PCM. 5Charge warning light in instrument cluster Comments: Is controlled by the PCM via the CAN databus. 6Temperature signal from IAT sensor 7Throttle control unit 8PCM relay The Smart Charging System comprises the following functions: Battery temperature calculation and charging voltage control Alternator load feed forward function Alternator deactivation on starting the engine Idle speed increase under low voltage / high electrical load conditions (to increase alternator output and reduce battery discharge) In the case of a conventional alternator, a fixed voltage value (setpoint value) is specified by the internal voltage regulator and used to control the system voltage. Although the voltage regulator functions of the alternator are retained with the Smart Charge system, the voltage setpoint is calculated in advance by the PCM. The Smart Charge system runs without any additional components, features a self-test function in the PCM and can be diagnosed using the Integrated Diagnostic System (IDS). Under high alternator load, the PCM can increase the idling speed above the basic idling speed in steps of up to 150 rpm, to increase the alternator output. After the engine has started, the alternator generates alternating current (AC) which it converts to direct current (DC) internally. The DC current is supplied to the battery and vehicle electrical consumers at a voltage regulated by the voltage regulator (located on the back of the alternator). The voltage of the charging system is controlled by the PCM. This is temperature-dependent. The battery is more efficiently charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM is able to adjust the charging voltage according to the battery temperature. The battery temperature is calculated on the basis of IAT and ECT. The PCM simultaneously monitors and controls the output voltage of the alternator. When the current consumption is high or the battery is excessively discharged, the system is able to increase the idle speed. To minimize engine drag torque when starting the engine, the PCM deactivates the alternator. After the engine has started, the PCM increases the alternator output until the required value is reached. The PCM controls the function of the charge warning light, which is located in the instrument cluster. The PCM is therefore responsible for ensuring that the charge warning light goes off after the engine has started and comes on in the event of a fault. The charge warning light is also activated by the PCM when the ignition is on, the engine is off and the engine stalls. The battery charging current is optimized through continuous calculation of the battery temperature and regulation of the alternator output voltage. The alternator load feed forward function informs the PCM in advance of imminent electrical loads, i.e. before the alternator torque changes. Based on this information, the PCM is able to guarantee greater idling stability. If the Smart Charge system is faulty, the voltage setpoint is adjusted to a value defined in the alternator. The charge warning light comes on in the event of faults in the system and if the charging voltage is too low.