P2D1D
Reductant System Leak Detected – Small Leak
The SCR module detects a small leak in the reductant system based on pressure decay rate after dosing pause. Slow loss of DEF/AdBlue.
- 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.
- Fitting or connection looseCommon
- Seal aged at injector or pumpPossible
Parts involved
- Reductant Lines
- Reductant Injector
- Reductant Pump
- SCR Module
P2D1D 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.