P207F
Reductant Quality Performance
The ECU has concluded that the AdBlue/DEF in the tank does not meet specification. Diagnosed by comparing expected NOx reduction against the dosed reductant volume — too much dosing for too little NOx drop indicates diluted or wrong fluid.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Common causes
Ordered by how often each turns out to be the cause.
- AdBlue diluted with water or wrong fluid filledCommon
- NOx sensor drift gives false reductant-quality verdictLess likely
Parts involved
- Adblue Tank
- NOX Sensor
- SCR Catalyst
P207F is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.