Code result
P204B
Reductant Pressure Sensor Circuit Range/Performance
Moderate severity
What it means
DEF pressure sensor reads within electrical range but plausibility fails — does not rise during prime, drift over a drive cycle, or stuck at a constant value.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Sensor drift or stuck reading
highOne of the most commonly reported causes for this code — check this first.
Pump pressure builds slowly
mediumA plausible cause — test and verify before replacing parts.
Sensor element aged beyond calibration window
lowLess common, but worth ruling out after the more likely causes.
Related help
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