Charging System Voltage Too Low (Non-OBD II)

Name of Code:
Charging System Voltage Too Low

When Monitored:
With the ignition key on and the engine running over 1500 RPM after 25 seconds.

Set Condition:
When the PCM regulates the generator field and there are no detected field problems but the voltage output does not increase.

Theory of Operation:
The PCM tries to maintain a system voltage between 12.9 volts and 15.0 volts. The voltage determined by the PCM as the final goal for the charging system is called "control" voltage. This control voltage is determined from the battery temp sensor (ambient sensor). The control voltage is compared to the sensed voltage continuously during running. The PCM controls battery voltage by energizing and de-energizing the alternator field winding. When the battery voltage falls below a setpoint voltage the generator field winding is energized until the battery voltage exceeds a setpoint voltage.

Possible Causes:
- Defects in generator drive belt or adjustment
- High resistance between battery (+) and generator (+) High resistance between battery (-) and generator ground
- PCM failure