P20CFExhaust Aftertreatment Fuel Injector A 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 doser that adds diesel to the exhaust for filter regeneration is judged to stay open, so fuel keeps flowing after the command to close. On Volvo and Mack trucks the nozzle sits right at the turbo outlet and is fed by an AHI module; their troubleshooting guide KC-2157 points first to the fuel supply and then to that module. For 2016 US14 trucks Mack and Volvo released software because the code logged without a confirmed fault. Ram lists P20CF on the 2025–2026 2500/3500 with the 6.7 L Cummins HO among the codes cured by a PCM update. Unburned fuel can overheat the catalyst or leave as white smoke. The opposite failure is P20D0.
- What you may notice
- Check engine light on
- White smoke or strong fuel smell from the exhaust
- Very high temperatures at catalyst and filter
- Higher fuel consumption
- Likely causes
- LikelyDirt or deposits holding the doser valve off its seat
- PossibleUpstream shutoff or dosing module letting fuel through
- PossibleCalibration error, fixed by a software update
- 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: €150 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.