Charging System - Generators & Regulators: Operation

The amount of amperage produced by the generator is controlled by Electronic Voltage Regulator (EVR) circuitry within the Powertrain Control Module (PCM). EVR circuity is connected in series with the generator field driver terminal and ground. A Battery Temperature Sensor (BTS), located in battery tray housing, is used to sense battery temperature. Sensed battery temperature and data from monitored line voltage is used by PCM to adjust battery charging rate. This is accomplished by cycling the ground path to control the strength of generator rotor magnetic field. PCM then compensates and regulates generator amperage output accordingly.

The PCM monitors critical input to control fuel injection, ignition, emission and other engine management functions. The PCM is also programmed to monitor charging system related circuits:

Battery feed to PCM.
Generator field control.
Battery charging voltage (high and low).

If a problem is sensed in a monitored circuit, a Diagnostic Trouble Code (DTC) will be stored in PCM memory and Malfunction Indicator Light (MIL) will illuminate, provided specific criteria have been met. DTCs can be read using MIL, Chrysler's Diagnostic Readout Box (DRBIII(R)), or a generic scan tool.

NOTE: DTC is erased from memory if failure does not reoccur after 40 engine starts.

Certain DTCs cause MIL to illuminate and PCM to enter limp-in mode. In limp-in mode, PCM uses a duty cycle of 25 percent. This allows some generator output until proper repairs are made.