DESCRIPTION - CHARGING SYSTEM
The charging system consists of:
² Decoupler Pulley (If equipped)
² Electronic Voltage Regulator (EVR) circuitry within the Powertrain Control Module (PCM)
² Ignition switch (refer to the Ignition System section for information)
² Battery (refer to the Battery section for information)
² Inlet Air Temperature
² Voltmeter (refer to the Instrument Cluster section for information if equipped)
² Wiring harness and connections (refer to the Wiring section for information)
² Accessory drive belt (refer to the Cooling section for more information)
OPERATION - CHARGING SYSTEM
The charging system is turned on and off with the ignition
switch. This voltage is connected through the
PCM and supplied to one of the generator field terminals
(Gen. Source +) at the back of the generator. The
alternator is internally grounded. The generator regulates
the field using Pin 1 of the field connector (High
The generator is driven by the engine through a serpentine
belt and pulley or decoupler pulley arrangement.
The PCM receives a voltage input from the alternator
and also a battery voltage input from the TIPM, it then
compares the voltages and if there is a difference it
send a signal to the alternator EVR circuit to increase
or decrease output. It uses a pulse width modulation
(PWM) to send signals to the alternator circuitry to
control the amount of output from the alternator. The
amount of DC current produced by the generator is
controlled by the EVR (electronic voltage regulator) circuitry contained within the alternator.
All vehicles are equipped with On-Board Diagnostics (OBD). All OBD-sensed systems, including EVR (electronic
voltage regulator) 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
Voltage is monitored at B+ stud to insure the cable is connected. If cable is loose PCM will shut down generator
field. Because of this new feature, pin 2 of the field connector is internally connected to the B+.
DIAGNOSIS AND TESTING
ON-BOARD DIAGNOSTIC SYSTEM
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
OBD system. Some circuits are checked continuously and some are checked only under certain conditions.
If the OBD system senses that a monitored circuit is bad, it will put a DTC into electronic memory. The DTC will stay
in electronic memory as long as the circuit continues to be bad. The PCM is programmed to clear the memory after
40 good trip if the problem does not occur again.
8F - 34 CHARGING PM
DIAGNOSTIC TROUBLE CODES
A DTC description can be read using the scan tool. Refer to the appropriate Powertrain Diagnostic Procedures manual
A DTC does not identify which component in a circuit is bad. Thus, a DTC should be treated as a symptom, not as
the cause for the problem. In some cases, because of the design of the diagnostic test procedure, a DTC can be
the reason for another DTC to be set. Therefore, it is important that the test procedures be followed in sequence,
to understand what caused a DTC to be set.
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