Charging System: Description and Operation
CHARGINGDESCRIPTION
The charging system consists of:
^ Generator
^ Generator decoupler pulley (if equipped)
^ Electronic Voltage Regulator (EVR) circuitry within the Powertrain Control Module (PCM)
^ Ignition switch
^ Battery (refer to Battery for information)
^ Battery temperature sensor
^ Generator lamp (if equipped)
^ Check gauges lamp (if equipped)
^ Voltmeter (refer to Instrument Cluster for information)
^ Wiring harness and connections (refer to Wiring for information)
OPERATION - CHARGING SYSTEM
On gasoline powered engines, the charging system is turned on and off with the PCM (Powertrain Control Module) and ignition switch with engine running. On diesel powered engines, the charging system is turned on and off with the ECM (Engine Control Module) and ignition switch with engine running. The field circuit will not be energized until engine is running and ignition switch on. This voltage is connected through the PCM and supplied to one of the generator field terminals (Gen. Source B+) at the back of the generator. The generator is internally grounded. The generator regulates the field using pin-1 of the field connector (high side driver).
The generator is driven by the engine through a serpentine belt and pulley, or a decoupler pulley arrangement.
The PCM, or ECM receives a voltage input from the generator (5) and also a battery voltage input (7) from the TIPM (Totally Integrated Power Module), it then compares the voltages to the desired voltage programmed in the EVR (Electronic Voltage Regulator) software, and, if there is a difference it sends a signal to the generator EVR circuit to increase or decrease output. It uses a Pulse Width Modulation (PWM) to send signals to the generator circuitry to control the amount of output from the generator. The amount of DC current produced by the generator is controlled by the EVR circuitry contained within the generator.
All vehicles are equipped with On-Board Diagnostics (OBD). All OBD-sensed systems, including EVR circuitry, are monitored by the PCM. Each monitored circuit is assigned a Diagnostic Trouble Code (DTC). The PCM will store a DTC in electronic memory for certain failures it detects.
The Check Gauges Lamp (if equipped) monitors: charging system voltage, engine coolant temperature and engine oil pressure. If an extreme condition is indicated, the lamp will be illuminated. This is done as reminder to check the three gauges. The lamp is located on the instrument panel. Refer to the Instrument Cluster section for additional information. Voltage is monitored at the B+ terminal stud to insure it is connected. If the B+ cable is loose, the PCM will shut down generator field. Because of this new feature, pin-2 of the field connector is internally connected to the B+ terminal.
The generator used with diesel engines is internally regulated. The generator and ECM communicate for diagnostics, etc. If the generator regulator becomes disconnected from the ECM, it will still operate, but in a default mode.
DIAGNOSIS AND TESTING
CHARGING SYSTEM
The following procedures may be used to diagnose the charging system if:
^ the check gauges lamp (if equipped) is illuminated with the engine running
^ the voltmeter (if equipped) does not register properly
^ an undercharged or overcharged battery condition occurs.
Remember that an undercharged battery is often caused by:
^ accessories being left on with the engine not running
^ a faulty or improperly adjusted switch that allows a lamp to stay on. Refer to Ignition-Off Draw Test in the Battery section for more information.
INSPECTION
The Powertrain Control Module (PCM) monitors critical input and output circuits of the charging system, making sure they are operational. A Diagnostic Trouble Code (DTC) is assigned to each input and output circuit monitored by the On-Board Diagnostic (OBD) system. Some charging system circuits are checked continuously, and some are checked only under certain conditions.
Refer to Diagnostic Trouble Codes in; Powertrain Control Module; Electronic Control Modules for more DTC information. This will include a complete list of DTC's including DTC's for the charging system. To perform a complete test of the charging system, refer to the appropriate Diagnostic Test Procedures and use a diagnostic scan tool. Perform the following inspections before attaching the scan tool.
1. Inspect the battery condition. Refer to Battery for procedures.
2. Inspect condition of battery cable terminals, battery posts, connections at engine block, starter solenoid and relay. They should be clean and tight. Repair as required.
3. Inspect all fuses in both the fuseblock and Power Distribution Center (PDC) for tightness in receptacles. They should be properly installed and tight. Repair or replace as required.
4. Inspect generator mounting bolts for tightness. Replace or tighten bolts if required. Refer to the Generator Removal/Installation section of this group for torque specifications.
5. Inspect generator drive belt condition and tension. Tighten or replace belt as required. Refer to Belt Tension Specifications in Cooling System.
6. Inspect automatic belt tensioner (if equipped). Refer to Cooling System for information.
7. Inspect generator electrical connections at generator field, battery output, and ground terminal (if equipped). Also check generator ground wire connection at engine (if equipped). They should all be clean and tight. Repair as required.
SPECIFICATIONS
GENERATOR RATINGS
TORQUE - CHARGING SYSTEM
