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 generator F terminal is a Pulse Width Modulated (PWM) duty cycle or load input to the PCM from the generator. As the generator load increases the PCM can sense the change and adjust the idle speed accordingly. 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 P0622 will set when either of the following condition are met:
^ F terminal duty cycle is less than 5% for 30 seconds when engine is running and engine speed is less than 3000 rpm.

Or

^ F terminal duty cycle is greater than 65% for 5 seconds and engine is not running.

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