P21CEReductant Quality Module Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Check engine light on
- DEF system error message in the display
- Erratic DEF level reading
- Likely causes
- LikelyContaminated or degraded DEF disturbing the measurement
- PossibleQuality module internally faulty
- PossibleCrystals or air bubbles on the sensing element
- RarePoor contact at the module connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €30 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.