Circuit Description

The L-terminal circuit No. 225 is the link between the ECM and generator. The ECM supplies the generator with 12 volts whenever the ignition is ON. Once engine is running, the generator must have the 12-volt supply to charge. If the engine is NOT running or the generator stops charging while the engine is running, it will ground this 12-volt supply from the ECM. When the ECM detects this low voltage state, it will send a message to the BCM over the Controller Area Network (CAN) link, which will send a message to the Instrument Panel (I/P) cluster over the Class 2 link to illuminate the charge telltale. DTC P1637 will set if the voltage at the generator L-terminal input is low when the engine is running.