P0625: A low generator F-terminal duty cycle is checked with the engine running

P0625 is a generator field/F-terminal circuit-low code. The cited GM monitor evaluates the filtered duty cycle of the F-terminal input. Its low threshold is a property of the monitored signal, not a direct statement that battery voltage fell below a charging-voltage limit.

A running check with a defined speed condition

The row identifies this as the F-terminal run test. Ignition must be on, the engine must be running and engine speed must be below 1,000 rpm. The documented failure criterion is filtered input duty cycle below five percent, with a five-second evaluation and one-trip reporting.

The same row also lists a condition associated with the terminal-L key-on test. It should remain identified as that separate prerequisite rather than being merged into the F-terminal failure threshold or translated into an invented battery-voltage requirement.

Match the measurement to the signal and state

Retain the F-terminal duty reading, engine-running state and speed during the event. A reading taken with the engine stopped cannot reproduce this running monitor. A battery-voltage trace may be useful in a wider charging investigation, but it does not directly measure the filtered signal the controller assessed here.

The table supplies no connector pin, alternator internal test or replacement conclusion. It cannot determine whether an abnormal duty result originates in signal generation, wiring or the receiving controller. The applicable charging-system procedure is needed to move from this scoped signal finding to an identified repair.

Source and applicability

2025 GM 07A-1 documented monitor only. Vehicle, engine and controller calibration applicability must be established separately; no model fitment is inferred from the file. GM PDF, physical page 925.