P20E8
Reductant Pressure Too Low
Pressure in the AdBlue/DEF supply line is below the target. Usually a failing reductant pump, a clogged filter, frozen lines, or a leak in the pressurised circuit.
- 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.
- Reductant pump weak or failedCommon
- Reductant filter clogged with crystalsPossible
- Leak in pressurised reductant linePossible
Parts involved
- Adblue Pump
- Adblue Filter
- Adblue Lines
P20E8 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.