Powertrain, generic (extended)

P206D Reductant Quality Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P206D is the upper limit counterpart of P206C. In GM's 2018 diesel table it is electrical: the piezo input of the ultrasonic quality sensor above 4.5 V in 40 of 50 samples, Type A. Ford's 2023 diesels set it when filtered urea concentration reads 60 % or more for over 900 s, which real DEF never reaches, so either the sensor or a foreign fluid is to blame. GM PIP5635 for 2019 Colorado and Canyon 2.8L names a false cause: urea crystals that form around the sensor when the fluid freezes and thaws. Before repairs, sensor status should read OK, concentration 28 to 40 % and the tank above 5 °C; if not, warm the truck indoors and drive it in traffic for 10 minutes. FCA STAR case S2025000006 for 2020 Wrangler and Gladiator diesels calls the code mainly electrical but asks for a refractometer and hydrocarbon strip test too.

Likely causes

Urea crystals around the sensor after freeze and thaw
Sensor signal open or shorted to voltage, failed sensor
Foreign or over-concentrated fluid in the tank

Symptoms

  • MIL and DEF or emission system warning
  • Fault often after cold nights
  • Countdown toward speed limit or no-restart

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–1,500
Time0.5–4 h

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

Parts involved

reductant quality sensor

Related codes

P206AP206BP206CP207F

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