P051E
Crankcase Pressure Sensor A Circuit Intermittent/Erratic.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 1E
- FaultThe specific fault in that area
What it means
P051E means the engine control unit has detected that the signal from crankcase pressure sensor A is intermittent or erratic. The signal keeps jumping, dropping out or changing in a way that does not fit a stable crankcase pressure, which points to a fault in the sensor circuit or the sensor itself rather than a steady out-of-range reading.
Symptoms
- Engine warning light on
- Rough or unstable idle
- Oil leaks from seals or gaskets if crankcase pressure is genuinely high
- Possible hesitation or reduced performance if the control unit uses a fallback value
- Occasional smell of oil or fumes from the engine bay
- Code that comes and goes with vibration or temperature
Possible causes
- Loose, corroded or damaged connector at the crankcase pressure sensorlikely
- Chafed, broken or intermittently shorting wiring between the sensor and the control unitlikely
- Failing crankcase pressure sensorlikely
- Fault in the sensor's reference voltage or earth supplypossible
- Blocked, restricted or faulty crankcase ventilation system causing genuinely fluctuating pressurepossible
- Oil contamination or moisture inside the sensor or connectorpossible
- Fault within the engine control unitrare
How to diagnose
- Read all stored codes and the freeze frame data, noting engine speed, load and temperature when the fault set, and look for related ventilation or pressure codes
- Inspect the sensor, its connector and the wiring for damage, oil contamination, corrosion, loose pins or chafing, and check the routing against heat sources and moving parts
- Clear the code and see how quickly it returns, then wiggle the connector and harness with the engine running while watching the live sensor reading for dropouts
- Compare the live crankcase pressure reading at idle and under load with the manufacturer's specification, as expected values vary by engine
- Check the sensor's reference voltage, earth and signal wire with a multimeter, and carry out a voltage drop test on the circuit
- Inspect the crankcase ventilation system, including hoses, breather and any separator, for blockage, splits, ice or sludge; the layout depends on the engine
- Check the pressure seen by the sensor is plausible by looking for signs of excessive blow-by, such as oil in the intake or leaks at seals
- Check for manufacturer service bulletins or control unit software updates relating to this code for the specific model
How to fix
- Clean, repair or replace the sensor connector and any damaged terminals
- Repair or replace damaged wiring in the sensor circuit
- Replace the crankcase pressure sensor if it is faulty or contaminated
- Clear blockages in the crankcase ventilation system and replace faulty hoses or components
- Repair the reference voltage or earth fault found during circuit testing
- Update the control unit software only if a known fault with the calibration is documented for the vehicle
Can I keep driving?
Short, gentle journeys are usually acceptable, but get it checked soon because a ventilation fault or high crankcase pressure can cause oil leaks and further wear. Stop driving if you see oil leaking heavily, the engine runs very roughly or other warning lights appear.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.