When the DTC P2500 OBDII code is stored, it means that the car’s computer found a lower-than-expected voltage signal in the generator lamp or alternator control circuit. The letter “L” in this code refers to the lamp control circuit.
The generator lamp belongs to the instrument panel. It warns the driver of possible charging system problems once it is illuminated. The continuity of its circuit is monitored by the PCM(Powertrain Control Module) when the vehicle is running.
The generator lamp control circuit is very important to the generator operation. Besides that, it maintains the battery charge levels.