P2D1FReductant System Flow - Restricted
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2D1F means DEF still moves, but less than the dosing command implies, typically because a filter, line or dosing valve tip is partly clogged. Stellantis lists it on 2025–2026 Ram 2500 to 5500 heavy-duty trucks together with P208B, P218F and P20E8 and advises a bucket test before replacing the doser: with doser fitted, pressure should hold 80–94 psi for over 6 minutes; with doser removed, 55–75 psi for over 30 s. Many returned dosers showed no fault. Ford's 2023 diesels detect clogging under P218F by correlating injection rate with pump duty. Plastic Omnium's patent reads a lower than expected pump speed as a clog sign. P2D20 is complete blockage.
- What you may notice
- Check engine light with exhaust fluid service message
- Code returns intermittently, often without a lasting fault
- Possible NOx efficiency code if dosing stays low
- Likely causes
- LikelyUrea crystals partly blocking the dosing valve nozzle
- PossibleClogged DEF pump filter or suction strainer
- PossibleKinked or pinched DEF line after body or exhaust work
- RareContaminated or aged DEF leaving deposits
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.