P204EReductant Pressure Sensor Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P204E covers a DEF pressure signal that jumps around although it stays inside the electrical limits, as with a loose terminal, a cracked wire or a sensor with an internal contact problem. GM's 2025 DEF controller is the public calibration: it adds up all absolute pressure changes over a moving window of 100 readings taken every 10 ms and counts a failure when that sum passes 1500 kPa while pumping forward, 1000 kPa when stopped or heating, or 200 kPa in reverse; ten failures within 100 runs store a Type A code. No other manufacturer documents the code in public. CARB expects input components to be checked for implausible as well as out-of-range signals. Besides the wiring, air in the line or a pump delivering unevenly can also make the pressure swing.
- What you may notice
- MIL on, fault may come and go
- Dosing interrupted at times
- Accompanying DEF pump or pressure codes
- Likely causes
- LikelyLoose or fretted terminal at the pressure sensor connector
- PossibleWire breaking intermittently under vibration
- PossibleAir in the DEF line or uneven pump delivery
- RarePressure sensor with internal intermittent fault
- 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: €50 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.