P20DBExhaust Aftertreatment Fuel Supply Control Stuck Open
- 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
- The supply valve that should isolate the exhaust doser from the fuel system stays open after being switched off, so the feed line remains pressurized when no regeneration is running. If the doser itself then leaks, fuel can reach the hot exhaust unasked. Ram names P20DB together with P20CF (doser A stuck open) on 2025–2026 Ram 2500/3500 trucks with the 6.7 L Cummins HO, where a PCM software update is the fix. Hino found that its fuel cut valve could hang and leave too much pressure trapped in the doser feed pipe, and released an improved valve. The circuit is fine here; stuck closed is P20DC, electrical faults P20D7, P20D9 and P20DA.
- What you may notice
- Check engine light on
- Fuel smell or smoke if the doser also leaks
- Long cranking after fuel system work
- Likely causes
- LikelySupply or fuel cut valve sticking open from wear or dirt
- PossibleDetection or control calibration error, fixed by software
- RareContaminated fuel leaving deposits in the valve
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.