P2043: Ford DEF tank temperature fails a cold-start comparison

Ford's P2043 monitor checks whether reductant tank temperature is plausible after an extended soak. The tank reading is expected to be close to ambient temperature. A difference greater than 20°C in either direction is the listed malfunction boundary.

Establish a genuine comparison opportunity

The engine-off time must be at least six hours and DEF level must be between 10 and 100 percent. Ford also limits the spread among ambient, SCR temperature and coolant temperature to 10°C. That supporting agreement helps establish that the environment has settled enough for the tank comparison to be meaningful.

Active P205C or P205D electrical temperature-sensor faults inhibit P2043. A circuit-range failure and a plausible-voltage-but-wrong-temperature result are therefore separate diagnostic branches.

Use the entire temperature snapshot

The source counts intermittent events per trip rather than giving a single fixed-duration road test. Preserve the cold-start tank, ambient and supporting temperatures together. The code does not prove contamination of DEF or a failed SCR catalyst. Determine why the tank reading disagrees using the correct sensor and shared-circuit diagnostic information, and verify under the required soak conditions after repair.

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 page 127. The documented monitor explains the fault decision; vehicle-specific service information is still needed for connector identification and a complete repair procedure.