Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P051C Crankcase Pressure Sensor A Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

5 V reference or signal line open or shorted to ground
Connector corroded or oily
Sensor faulty
5 V reference pulled down by another sensor

Symptoms

  • Check engine light on
  • Usually no change in driving
  • Disconnection check P04DB suspended

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–200
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

crankcase pressure sensorsensor wiringengine control module

Related codes

P051AP051BP051DP051EP04DB

References: fordservicecontent.com, static.nhtsa.gov.