P204FReductant System Performance (Bank 1)
- 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
- P204F (Bank 1) is the functional check of the whole DEF delivery path: the parts are electrically intact, yet the system cannot build or hold the pressure needed for dosing. GM's 6.6 L LML stores a Type A code if the pump module stays at or below 350 kPa after 30 build-up and venting attempts of at least 10 s each; the 2014 Cruze diesel uses 375 kPa and 20 attempts. GM treats P204F as a tamper fault. On Hino trucks P204F is the engine ECU's summary code for urea SCR faults seen by the dosing unit; per TT-14-025 it clears only after the DCU faults are repaired and the SCR memory has been reset. Ram's 3.0 L V6 EcoDiesel received PCM updates covering it (18-008-21). CARB demands this delivery check. Causes include frozen or clogged lines, a worn pump, air leaks or an empty tank.
- What you may notice
- MIL and DEF warning on
- Countdown to speed or power limitation
- Code returns after clearing until the cause is fixed
- Likely causes
- LikelyDEF line clogged by crystals or frozen
- PossibleWorn DEF pump that cannot reach target pressure
- PossibleAir leak on the suction side or loose line couplings
- PossibleDosing unit faults repaired but SCR memory not reset (Hino)
- RareControl module software needing an update (Ram 3.0 L)
- 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 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.