Circuit/System Description

The engine control module (ECM) uses the charge indicator signal circuit, or L-terminal circuit, to control the load of the generator on the engine. A high side driver in the ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the charge indicator signal circuit. If the ECM detects that the charge indicator signal circuit is shorted to ground or voltage, DTC P0621 will set.