P203A: Ford DEF level-sensor open-load circuit fault

Ford's 2015 diesel summary maps P203A to an open-load fault in the reductant tank level-sensor circuit. The power stage sends the fault information directly; the document does not provide a separate voltage threshold for this code. It must therefore be distinguished from the neighboring high- and low-voltage range checks.

The shared ground is useful evidence

Ford states that the reductant level sensor and tank-temperature sensor share a ground wire. An open load or short to battery on that reference path can produce faults for both sensors. When level and temperature codes occur together, that documented shared connection is a meaningful diagnostic lead rather than proof that two sensors independently failed.

The level monitor works in a four-second cycle: three individual pin readings followed by diagnosis. The listed 0.5-second fault-registration time applies within diagnostic mode, not the complete sampling cycle.

Separate wiring from actual fluid level

P203F concerns insufficient reductant level; P203A concerns the electrical measurement path. Refilling the tank does not establish that an open-load circuit has been corrected. Use the exact tank-sensor wiring and service tests to isolate the fault. The summary does not authorize a sensor or tank assembly replacement from this code alone.

Source and applicability

Ford 2015 model-year diesel OBD system operation summary, revision December 22, 2014; the cited monitor only, without blanket model or engine applicability. Ford source, physical PDF pages 19, 125. The documented monitor explains the fault decision; vehicle-specific service information is still needed for connector identification and a complete repair procedure.