P206BReductant Quality Sensor 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
- P206B means the quality sensor answers, but its result cannot be used or does not fit what the SCR system does. GM sets it in its 2018 diesel table when the DEF controller keeps reporting the sensor as not ready, for instance because the ultrasonic echo is lost on a fouled sensor: 200 failed out of 250 samples, Type A, checked only with over 4 L of DEF and a sensor above 5 °C. GM bulletin 18-NA-124 for the 2018 Equinox and Terrain 1.6L diesel traces many cases to micro-bubbles from aerating filling equipment. Ford's 2023 diesels log an internal sensor error under P206B. Hino tests rationality: NOx conversion well below target while the sensor still claims usable fluid sets P206B with MIL. FCA lists it for its 3.0L diesels, and Ford SSM 51891 links it on 2023 Super Duty trucks with U02A2 and connector checks.
- What you may notice
- MIL and Service Emission System or DEF message
- Fault appears shortly or hours after refilling DEF
- Possible countdown to speed limit
- Likely causes
- LikelyAir bubbles on the sensor after filling
- PossibleDeposits or crystals on the ultrasonic sensor
- PossibleInternal fault in the quality sensor or tank module
- RareDrifting NOx sensor upsetting the rationality check (Hino logic)
- 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 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.