Circuit Description

The PCM controls generator charging by supplying the generator a control voltage of 5 volts whenever the ignition is turned ON or engine is running. This control voltage is necessary for the generator to charge once the engine has started and the generator begins to spin. With the ignition ON, engine OFF, the generator will ground the control voltage through a pull-down resistor. The voltage on circuit No. 25 with the circuit intact will read between 1.0-1.5 volts. When engine is started and generator begins to charge, the generator will open the circuit, still using the 5-volt control voltage, signaling to the PCM that the generator is charging. DTC P0621 sets when the engine is running and the voltage at the PCM generator L-terminal output is low indicating the generator is not charging or circuit No. 25 is shorted to ground. If this condition occurs, the PCM will send a message to the I/P cluster over the Class II link to turn ON the charge (battery) telltale.