Powertrain, generic (extended)

P206C Reductant Quality Sensor Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P206C is the low-side fault of the quality sensor, read in two ways. GM treats it as electrical: in its 2018 diesel table the piezo input of the ultrasonic sensor below 0.15 V in 40 of 50 samples sets the code, Type A. Ford uses it as a quality verdict: its 2023 diesels flag P206C when the filtered urea concentration stays at 28 % or less for over 900 s, and Ford SSMs 46890 to 50323 for 6.7L, 3.2L and 3.0L diesels say most cases come from diluted DEF, so the fluid is checked with a refractometer and replaced before parts are swapped, since low concentration also triggers a derate. GM PIP5602 for 2019 Colorado and Canyon 2.8L adds a false trigger: at roughly 30 % fill or less, a long right-hand curve can uncover the sensor; no parts are replaced, the tank is simply filled. Above-range readings belong to P206D.

Likely causes

Diluted or wrong fluid in the DEF tank (Ford definition)
Low tank level letting the sensor run dry in curves
Sensor signal shorted to ground or failed sensor element

Symptoms

  • MIL and DEF quality or emission system warning
  • Reduced power or speed limit on Ford diesels
  • Warning that appears after a long curve and then clears

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–1,500
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant quality sensor

Related codes

P206AP206BP206DP207F

References: gsi.ext.gm.com, fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov.