Circuit DescriptionThe crankcase pressure sensor is used to monitor the pressure inside the crankcase. The engine control module (ECM) supplies the crankcase pressure sensor a 5 volt reference voltage. When the crankcase pressure is low, the sensor signal voltage is low. When the crankcase pressure is high, the sensor signal voltage is near the 5 volt reference voltage. The ECM monitors the crankcase pressure signal circuit voltage to calculate the pressure of the air within the crankcase.

Component LocationThe crankcase pressure sensor is located near the crankcase ventilation element.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault CodesThe ECM detects that the crankcase pressure is greater than a calibrated value.

Action Taken When the Fault Code is ActiveThe ECM illuminates the red CHECK ENGINE lamp immediately after the diagnostic runs and fails.The engine torque output will be reduced to protect the engine from excessive crankcase pressure.Conditions for Clearing the Fault CodeTo validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop-and-go city-type driving and steady-state highway-type driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.To validate the repair using a Chassis Dynamometer, utilize a routine that incorporates acceleration and motoring events, steady-state highway-type operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.The ECM will turn off the red STOP ENGINE lamp immediately after the diagnostic runs and passes.The Reset All Faults command in INSITE? electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop TalkPossible causes of this fault code include:

Crankcase breather element may be pluggedCrankcase pressure sensor damagePlugged or restricted crankcase breather oil separatorPlugged or restricted crankcase breather oil drain tube or check valvePlugged or restricted crankcase breather draft tubeFrozen, plugged, or restricted crankcase breather tube.It is important to check for plugged or restricted hoses, tubes, check valves, oil separator, and filters in extreme cold ambient temperatures. If Fault Code 555 becomes active due to a plugged filter before the maintenance interval is reached or the filter plugs frequently, see the Crankcase Gases (Blowby) Excessive troubleshooting symptom tree in Section TS.

Possible Cause:1) Crankcase pressure sensor failure2) Crankcase breather filter element failure3) ECM calibration