P20F5
Reductant Consumption Too High
The DEF consumption observed over the dosing window is above the model expectation — typically a leaking injector seat, leaking line fitting, or a pressure-control valve that vents constantly to the tank.
- 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.
- Injector seat leaks DEF into exhaustCommon
- Cracked line or fittingPossible
Parts involved
- Reductant Injection Valve
- Reductant Supply Line
- Reductant Pressure Control Valve
P20F5 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.