Normal Operation: Notes

The PCM monitors the generator output via the GENMON circuit (generator field terminal circuit). If the PCM cannot read the GENMON circuit due to an open or short to ground, when the engine rises above approximately 2, 000 RPM, the generator will default to a steady voltage of approximately 13.5 volts and the PCM will send a request to the Instrument Cluster (IC) to illuminate the charging system warning indicator. A GENMON duty cycle of 3% or less indicates a short to ground fault is present and will result in DTC P0625 setting in the PCM. A GENMON duty cycle of 98% or more indicates an open or short to voltage fault is present and will result in DTC P0626 setting in the PCM.

• DTC P0625 (Generator Field Terminal Circuit Low) - If the GENMON circuit is shorted to ground, the A sense circuit is open or the B+ circuit is open, the PCM will set this DTC. This DTC can also be set by a faulted PCM or generator.
• DTC P0626 (Generator Field Terminal Circuit High) - If the GENMON circuit is open or shorted to power, the PCM will set this DTC. This DTC can also be set by a faulted PCM or generator.

This pinpoint test is intended to diagnose the following: 

• Fuse
• Wiring, terminals or connectors
• Radial arm adapter
• Engine, generator and battery grounds
• Battery
• Generator
• PCM