Powertrain, generic (extended)

P21CE Reductant Quality Module Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P21CE says the DEF quality module as a unit is not working properly: it is supplied and talking to the controller, but its self-test or the plausibility of its output fails, so the controller cannot rely on the concentration it reports. This differs from P206B to P206D, which grade the measured concentration, and from P21CD, which concerns the module supply. Nissan uses P21CE on the 2019 Titan XD with the Cummins 5.0 L V8, often with P1349 for an erratic tank level, and a DEF system message may appear. Bulletin NTB20-005 has the technician follow the normal diagnosis and, if it leads to part replacement, first drain the tank and refill it with fresh fluid, reinstalling the pump with a new seal. Ford's 2023 diesel summary reports an internal quality sensor error as P206B instead.

Likely causes

Contaminated or degraded DEF disturbing the measurement
Quality module internally faulty
Crystals or air bubbles on the sensing element
Poor contact at the module connector

Symptoms

  • Check engine light on
  • DEF system error message in the display
  • Erratic DEF level reading

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€30–1,500
Time0.5–3 h

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

Parts involved

reductant quality sensor

Related codes

P21CDP206BP206CP206DU02A2

References: static.nhtsa.gov, fordservicecontent.com, law.cornell.edu.