P204D: Reductant Pressure Sensor Circuit High
Standardized SAE J2012 code · P20xx — Fuel & air metering and auxiliary emission controls
What does P204D mean?
DEF pressure sensor reads above the upper plausibility limit — open signal or short to B+. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Common causes
- High Open signal line
- Low Connector pins corroded - high contact resistance
- Low Supply wire pinched against B+ source
Likelihood is a general estimate across vehicles; your make and model may differ.
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