OBD-II code · Powertrain (generic, extended)
P204C Reductant Pressure Sensor Circuit Low
DEF pressure sensor reads below the lower plausibility limit — short to ground or sensor element shorted.
Is it safe to drive with P204C?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyShort to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
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)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–2 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Pressure Sensor
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.