P051C
Crankcase Pressure Sensor A Circuit Low
Crankcase ventilation
Generic OBD-II
High
What it means
P051C means the crankcase pressure sensor's signal is reading lower than the valid range, usually from a short to ground, an open wire, or a failing sensor. This sensor monitors pressure inside the crankcase to help watch the positive crankcase ventilation (PCV) system. It's mostly a monitoring fault, so the engine typically runs and starts normally.
High
Can I keep driving? Usually yes — the car generally runs and starts normally; this is mainly a sensor/monitoring fault, but have it checked to protect crankcase ventilation.
Common symptoms
What you'll notice
- Check-engine light on
- Often no noticeable change in how the car drives
- Possible related PCV/crankcase ventilation codes stored
- Rarely, a faint oil smell if a PCV problem is also present
Common causes
Most likely first
- Short to ground or open in the crankcase pressure sensor signal circuitLikely
- Faulty crankcase pressure sensorCommon
- Corroded or loose sensor connectorCommon
- Damaged sensor supply or ground wireLess often
- ECM signal-processing fault (least common)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and view the crankcase pressure sensor's live voltage.
- Inspect the sensor connector and wiring for a short to ground, corrosion, or damage.
- Check the sensor's reference voltage and ground against spec.
- Replace the crankcase pressure sensor if it reads low with good wiring.
- Clear the code and confirm the circuit reads within range.
FAQ
Quick answers
Is it safe to drive with P051C?+
Generally yes, since it's mainly a sensor circuit fault and the engine usually runs normally. Have it checked so crankcase ventilation stays properly monitored.
Can I just clear P051C?+
It clears, but returns if the sensor or its wiring is still reading low. Repair the circuit or replace the sensor first.
Related codes
Often seen with P051C
Read & clear P051C yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX