P204BReductant Pressure Sensor Circuit Range/Performance
- 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
- P204B is a plausibility test: the DEF pressure sensor is electrically fine, but its value disagrees with the system state. GM uses moments when the true pressure is known. The 6.6 L LML sets it if more than 50 kPa appears while the line is empty and unpressurised (Type A, Type B on the 2014 Cruze diesel); GM's 2018 diesel table compares the reading with ambient after the end-of-trip purge, and GM's 2025 DEF controller fails it when the value strays more than 36.4 kPa from ambient before priming. Deutz marks the case on the EMR L1 with failure type 64. Hino released new DCU software in 2016 (SB-16-015) because the unit stored P204B falsely on conventional trucks. A genuine offset mostly means an ageing sensor in the pump module.
- What you may notice
- MIL on, possibly only after a second trip
- Emission service message
- Often no noticeable driveability change
- Likely causes
- LikelyPressure sensor offset drift inside the pump module
- PossibleDosing control unit software misjudging the reading (Hino SB-16-015)
- PossibleLine not emptied at shutdown, e.g. afterrun interrupted or frozen DEF
- 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: €0 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.