Voltage Signal: Description and Operation

The engine controller monitors battery voltage to determine the proper injector pulse width and to control the alternator field voltage. If the engine controller sees low battery voltage, it will increase the injector pulse width to compensate for lack of voltage which could cause a lean air/fuel mixture. It will also send a higher voltage signal to the alternator field so that the alternator will increase its charging output to the battery. When the alternator increases its charging rate it will bring the battery up to its normal state of charge. Once the battery is fully charged, the engine controller reduces the injector pulse width so that the air/fuel mixture doesn't go excessively rich.

The engine controller continuously monitors battery voltage inputs, and since battery voltage always fluctuates, the engine controller will constantly be making changes to the injector pulse width and alternator field.