Some 2017-2021 F-Super Duty and 2016-2021 F650-750 with 6.7L diesel engines, 2015-2019 Transit with 3.2L diesel engines and 2018-2021 F-150 with 3.0L diesel engines may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble code (DTC) P206C in the powertrain control module (PCM). Review of repair data supports that P206C is often the result of incorrect diesel exhaust fluid (DEF) concentration. Per Powertrain Control/Emissions Diagnosis (PC/ED) Pinpoint Test (PPT) RJ, a DEF concentration reading below 28% will set P206C and cause vehicle derate. If low concentration is suspected, drain fluid and replace with known good DEF before replacing any parts. Low concentration of DEF is not a warrantable condition.
