P0C27: Auxiliary-pump undercurrent is a decoded operating report, not feedback duty low

P0C27 is Ford's auxiliary transmission-fluid pump undercurrent report, paired with P0C26_18. The controller is receiving a category about pump current. That is different from saying the feedback wire's duty cycle is electrically low.

Separate the report from the communication format

The same table assigns feedback frequency and duty-cycle faults to P0C2C, P0C2D and P0C2E. Those signal checks have their own frequency and duty criteria. A valid feedback pulse train can therefore carry a pump operating report that is still abnormal.

Ford also lists incorrect speed separately as P0B0D and combined current-and-speed disagreement as P0C29. Undercurrent should not be silently renamed as underspeed or as the combined performance result. The detailed code helps preserve what the module actually reported.

Retain command and status together

A useful record contains the exact suffix, commanded pump operation and the reported current/speed categories available from the module. A current reading without the operating state may answer a different question from the controller's stored undercurrent classification.

The summary does not publish a universal amperage threshold or identify an open winding, weak supply or failed module as the cause. It also gives no external powering procedure. Verification needs the matched pump-control information to establish the operating discrepancy while separately checking whether the feedback signal itself is valid.

Source and applicability

Ford 2024–2025 gasoline OBD operation summary, July 16 2024 revision; only the cited monitor and transmission architectures. No individual vehicle fitment or universal calibration is inferred. Ford PDF, page 156. Ford PDF, page 160.