P20E0
Reductant Pressure Too Low
The pressure in the SCR reductant (AdBlue/DEF) line is below the calibrated minimum. Without sufficient pressure the dosing module cannot atomise reagent properly, leading to NOx exceedence.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
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.
- Worn DEF pumpCommon
- Leak in DEF linePossible
- Clogged DEF filterPossible
Parts involved
- Def Pump
- Def Pressure Sensor
- Def Lines
P20E0 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.