P04C5: lock-position signal is low rather than simply unlocked

P04C5 concerns low feedback from the fuel-fill door lock-position sensor or switch in the cited GM hybrid table. The strategy classifies this as a short-to-ground diagnostic and compares the reported position with a low threshold.

Electrical low is not a normal lock state

A legitimate unlocked indication and an invalid low circuit reading are different concepts. The code is not established simply because the mechanism is unlocked. It indicates that the monitored electrical representation has fallen outside the accepted range.

The fuel-door position channel has its own low-circuit code, P04B9. P04C5 belongs to lock-position feedback. A diagnostic report should name that channel explicitly so the technician does not inspect the wrong switch or apply the wrong wiring information.

A secondary absence can be misleading

The lock and unlock performance checks list this electrical fault among their exclusions. If P04C5 is active, lack of a separate movement-performance code cannot be used to certify the actuator. The controller may be unable to trust the state needed for that evaluation.

The low result requires multiple failing samples with the diagnostic calibration enabled. Capture whether the input remains low, changes with operation or becomes intermittent; those observations help guide the appropriate circuit test but do not identify a failed part on their own.

Use the vehicle-specific diagram and service limits for electrical measurement. The percentage threshold in the summary is a controller-reported value, not an instruction to probe a terminal for that numerical percentage.

Application limits

Document-level 2015 GM diagnostic table; per-code vehicle/engine/calibration applicability not established.

Source

15OBDG01 Hybrid Diagnostics, physical PDF pages 595.