P051C code meaning
Crankcase Pressure Sensor A Circuit Low
Powertrain system Generic code P05xx codes Check engine light
What P051C means
The crankcase pressure sensor measures pressure in the crankcase ventilation (PCV) against atmosphere; Ford's EcoBoost engines use it for the disconnection check P04DB, which needs a sound sensor. P051C means the signal of the analogue ratiometric sensor is too low – Ford sets it below 0.44 V for 5 s. Typical is a signal shorted to ground, an open or shorted 5 V reference, or an open signal line pulled down.
P051C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P051C
- Check engine light on
- Usually no change in driving
- Disconnection check P04DB suspended
Common causes of P051C
- Most likely5 V reference or signal line open or shorted to ground
- PossibleConnector corroded or oily
- PossibleSensor faulty
- Less likely5 V reference pulled down by another sensor
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Crankcase pressure sensorSensor wiringEngine control module
What each part of P051C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 1C | The exact fault in that area. |
What to do next
- Note P051C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P051C
What does P051C mean?
P051C means "Crankcase Pressure Sensor A Circuit Low". The crankcase pressure sensor measures pressure in the crankcase ventilation (PCV) against atmosphere; Ford's EcoBoost engines use it for the disconnection check P04DB, which needs a sound sensor. It is a generic code, so it means the same on every make.
Is it safe to drive with P051C?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P051C fail an emissions test?
Yes, it can. P051C is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P051C to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P051C clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.