Powertrain Diagnosis

Diagnostic Chart:

Schematic:

The generator communicates to the Powertrain Control Module (PCM) over two circuits, the (L) or Lamp circuit and the (F) or Field circuit. The PCM uses the L circuit to monitor faults in the charging system. The generator L terminal indicates whether the PCM is allowing the generator to operate. The PCM can disable the generator under certain conditions in order to ease starting. Active indicates that the PCM is allowing generator operation, while inactive indicates that the PCM is not allowing generator operation. If the internal regulator in the generator detects a charging system fault the regulator grounds circuit 225. The PCM then sends a Class 2 message to turn On the charge telltale.

DTC PARAMETERS
DTC P0621 will set when either of the following conditions have been met:
^ Engine running and generator L terminal is low for 15 seconds.

- OR -

^ Engine is not running and generator L terminal is high for 5 seconds.

DIAGNOSTIC AIDS
Use Scan tool to command generator L terminal On and Off while monitoring generator F terminal DC.