Description And Operation: Notes
DESCRIPTION
The charging system consists of the following components:
| 1. | Refer to POWERTRAIN CONTROL MODULE (PCM) with an integrated Electronic Voltage Regulator (EVR). |
| 2. | Refer to GENERATOR . |
| 3. | Refer to INTELLIGENT BATTERY SENSOR (IBS) . |
| 4. | Refer to POWER DISTRIBUTION CENTER (PDC) . |
| 5. | Refer to BODY CONTROL MODULE (BCM) . |
| 6. | Refer to INSTRUMENT PANEL CLUSTER (IPC) . |
STANDARD GENERATOR SYSTEM OPERATION
The Electronic Voltage Regulation (EVR) system maintains the system voltage at a desired level by turning the Pulse Width Modulated (PWM) generator field control circuit (A) on and off. When the generator field is turned on, the system voltage increases. When the generator field is turned off, the system voltage slowly drops. The rate at which this happens is dependent upon the existing electrical loads, ambient under hood temperature, and the engine speed. A constant system voltage (B, C, D) can be maintained only when the generator field is switched on and off at a duty cycle that very accurately emulates the existing electrical loads given the existing ambient under hood temperature and engine speed.
During normal operation, the voltage reading at the generator output stud will be very close to the target charging voltage viewed on the scan tool. This is the system voltage and is sensed by the PCM through the fused B+ circuit (B). With the generator connector plugged in, the voltage reading on the generator sense circuit will be approximately 3.5 volts less than the voltage at the generator output stud due the resistor inside the generator. This is the generator sense (E) input to the PCM. These two voltage sense inputs are used and compared during the different diagnostics performed on the EVR System by the PCM.
In diagnostic mode, when the PCM detects that the output voltage is too high or too low, the PCM runs a series of diagnostics to determine the cause. When the diagnostic is initiated, the PCM will change the field control circuit and look for a change in the output voltage. If no reaction is detected, the PCM rationalizes that it has lost control of the generator field control (A) due to an open or shorted condition. If the generator field control is active, and the engine speed is above a calibrated threshold, the PCM will run a series of tests that turn the generator field control off and on for a brief period of time and monitors the system voltage (B) for a calibrated amount of change in the voltage, to determine a failure of the generator. This diagnostic test requires repeated failures to insure that an erroneous fault is not set.