P204DReductant Pressure Sensor Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P204D is the high-side counterpart: the pressure signal sits near or above the supply voltage, typically because the signal wire touches 5 V or battery voltage, the sensor ground is open, or the sensor has failed internally. Published limits are 4.80 V on GM's 6.6 L LML, 98 % of the supply in GM's 2018 diesel table, 4.90 V in GM's 2025 DEF controller and 4.85 V on Ford's 2023 diesels. GM's 2014 Cruze diesel logs it as Type B, the other GM tables as Type A. Deutz's EMR L1 calls the same state a short circuit to battery. To the controller such a reading could look like over-pressure, which is why it stops the pump; check the connector at the pump module and the sensor ground before replacing the module.
- What you may notice
- MIL on (after two trips on some GM diesels)
- DEF pump stopped, no dosing
- DEF warning and later inducement
- Likely causes
- LikelyOpen sensor ground or corroded ground terminal
- PossibleSignal wire shorted to 5 V reference or battery voltage
- PossibleInternal failure of the pressure sensor in the pump module
- 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: €60 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.