Crankcase Pressure Sensor Circuit Low
The P051C code indicates that the Engine Control Module (ECM) has detected a voltage signal from the crankcase pressure sensor that is lower than the expected range. This sensor monitors pressure inside the crankcase to detect excessive blow-by gases, which can indicate worn piston rings or other internal engine issues. A low voltage reading typically points to a short to ground, a faulty sensor, or a wiring problem.
01. Most Common Causes
- Faulty crankcase pressure sensor
- Short to ground in sensor circuit
- Open or damaged wiring/connector
- Corroded or loose electrical connections
- ECM internal fault (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or engine misfire
- Decreased engine performance
- Increased oil consumption
- Possible oil leaks from seals
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P051C and check for related codes.
Step 2: Visually inspect the crankcase pressure sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test sensor voltage reference and ground at the connector using a multimeter (typically 5V reference, good ground).
Step 4: Measure sensor signal voltage with engine off and running; compare to manufacturer specs.
Step 5: If signal is low, disconnect sensor and check for short to ground in the signal wire.
Step 6: Replace sensor if all wiring tests pass; clear code and test drive.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a low crankcase pressure sensor circuit can lead to undetected engine damage, such as excessive blow-by or oil leaks, potentially causing catastrophic engine failure.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor. The sensor itself is usually $20-$50, and labor is about $30-$100 depending on the vehicle.