P21AEReductant Level Sensor C Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P21AE stands for an implausible level sensor C signal whose voltage is still electrically valid. No manufacturer describes a separate check for this code in public material. GM shows how such plausibility testing can work: on the 2014 Cruze diesel the ECM compares the readings of all three discrete level sensors after the test pulse and flags combinations that cannot physically occur together, but files the result under P203B rather than under a code for the sensor concerned. For the 2018 Cruze, GM did assign P21A9 to sensor 2. A maker using P21AE would point to sensor C itself, for instance after urea crystal deposits or partial freezing. Electrical faults of this sensor are covered by P21AF and P21B0.
- What you may notice
- Check engine light on
- DEF level display does not match the refill amount
- Possible DEF warning sequence
- Likely causes
- PossibleCrystallised urea on level sensor C
- PossiblePartly frozen fluid around the sensor
- RareLevel sensor C drifting or degraded
- 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: €0 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.