P2D20Reductant System Flow - Blocked
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2D20 is the hard verdict after P2D1F: no measurable DEF passes, so the pump keeps pressure but nothing reaches the exhaust. A public manufacturer description of P2D20 does not exist; GM's 2025 diesel tables flag the matching symptom under P20E9 when DEF pressure stays more than 63 kPa above its setpoint for 4 s during closed loop control (Type A). Ford's 2023 diesels check flow plausibility under P218F and the dosing valve itself under P208E, stuck closed. California requires the delivery system to be monitored because without reductant the SCR catalyst stops reducing NOx. Frozen fluid, a fully crystallised nozzle or a closed valve are typical. Expect a fast countdown to reduced speed.
- What you may notice
- Check engine light and DEF warning, often in frost
- Countdown to speed limitation or start inhibit
- Follow-up NOx efficiency codes
- Likely causes
- LikelyDosing valve stuck closed or nozzle fully crystallised
- PossibleFrozen DEF in line or valve due to a failed line heater
- PossibleCrushed or fully kinked DEF line
- RarePump filter completely blocked by 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: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.