Charging System

The charging system consists of:

Generator Electronic Voltage Regulator (EVR) circuitry within the Powertrain Control Module (PCM) Ignition switch Battery (refer to BATTERY SYSTEM - SERVICE INFORMATION article for information) Battery temperature sensor Generator Lamp (if equipped) Check Gauges Lamp (if equipped) Wiring harness and connections (refer to SYSTEM WIRING DIAGRAMS article for information)

1 - PCM 2 - TIPM 3 - Battery

4 - Generator 5 - Feed Back Circuit B+ 6 - Control Circuit 7 - Battery Sense

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 programed 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.

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.

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.

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.

To perform a complete test of the charging system, use a diagnostic scan tool. Perform the following inspections before attaching the scan tool.

1. Inspect the battery condition. Refer to BATTERY SYSTEM - SERVICE INFORMATION article 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 fuse block 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 GENERATOR for torque specifications. 5. Inspect generator drive belt condition and tension. Tighten or replace belt as required. Refer to Belt Tension Specifications inSPECIFICATIONS . 6. Inspect automatic belt tensioner (if equipped). Refer to COOLING article 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.

DENSO 180 2.8L Diesel

The Electronic Voltage Regulator (EVR) is not a separate component. It is actually a voltage regulating circuit located within the Powertrain Control Module (PCM). The EVR is not serviced separately. If replacement is necessary, the PCM must be replaced.

The amount of DC current produced by the generator is controlled by EVR circuitry contained within the Powertrain Control Module (PCM). This circuitry is connected in series with the generators second rotor field terminal and its ground.

Voltage is regulated by cycling the ground path to control the strength of the rotor magnetic field. The EVR circuitry monitors system line voltage (B+) and battery temperature. It then determines a target charging voltage. If sensed battery voltage is 0.5 volts or lower than the target voltage, the PCM grounds the field winding until sensed battery voltage is 0.5 volts above target voltage. A circuit in the PCM cycles the ground side of the generator field up to 100 times per second (100Hz), but has the capability to ground the field control wire 100% of the time (full field) to achieve the target voltage. If the charging rate cannot be monitored (limp- in), a duty cycle of 25% is used by the PCM in order to have some generator output. Also refer to OPERATION for additional information.