P04C0: fuel-door unlocking failed to produce the expected transition

P04C0 is the fuel-fill door unlock performance result in the cited GM hybrid table. The controller requests unlocking, the mechanism is not already reported unlocked, and the expected locked-to-unlocked transition fails to appear during the evaluation.

An unlock request is not proof of release

The command is only one part of the evidence. The controller also needs feedback showing that the state changed. A scanner can display an unlock request even if the actuator did not move or the feedback did not reflect that movement.

The published row specifies a 600-millisecond check for this calibration. It also requires the dedicated diagnostic enable. Those qualifications explain why an isolated button press outside the proper controller state is not a complete reproduction of the test.

Separate the direction of failure

P04BC covers failure to lock; P04C0 covers failure to unlock. A mechanism that works in one direction has not automatically demonstrated the other direction. Preserve the exact transition associated with the stored result.

The monitor excludes several related driver and position-circuit faults. Resolve whether those conditions prevented a valid performance evaluation before interpreting a non-returning code as a repair.

The summary supplies no approved force-release or bypass method. A stuck fuel door needs the vehicle's documented access and repair procedure. Diagnostic records should retain the command, starting position and subsequent feedback so that electrical, mechanical and reporting problems can be distinguished.

Application limits

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

Source

15OBDG01 Hybrid Diagnostics, physical PDF pages 594.