Positive Crankcase Ventilation (PCV) System Diagnostics (Turbocharged Engines)

TURBOCHARGED SYSTEM 

The Powertrain Control Module (PCM) monitors the dirty air (PCV valve) and clean air (Make Up Air/MUA) sides of the crankcase ventilation system for disconnects. The monitoring strategies are explained in the component service information below.

DIAGNOSTICS - DIRTY AIR (PCV Valve) SIDE 

• The dirty air side of the system does not have a sensor for detecting a hose disconnect. A disconnected PCV tube will cause a measurable vacuum leak and likely idle quality issues. However, the range of authority of torque management can keep engine rpm in control despite a disconnected PCV tube causing a vacuum leak. To diagnose this condition, an algorithm using the gas flow/air flow ratio is calculated and compared to a calibrated threshold. If the diagnostic is determined to be failing, a DTC (P04FC)  is set.
  NOTE:

  Since this diagnostic uses the calculated gas flow/air flow ratio to make a determination of a failure, any issue that effects the pressure in the intake manifold can cause this fault to set.

DIAGNOSTICS - CLEAN AIR (MUA) SIDE 

• If the MUA tube is disconnected from the Air Induction System tube, PCV vapors will leak into the atmosphere whenever the engine is in boost. The Crankcase Pressure Sensor is used to diagnose a disconnect in the MUA Tube. The Crankcase Pressure Sensor is part of the MUA tube assembly. The PCM monitors the pressure pulsations in the Crankcase Pressure Sensor signal to determine whether or not the hose is connected. If the MUA tube is determined to be disconnected, a DTC (P2C90)  is set. The PCM also monitors the sensor and circuits for electrical faults such as opens or shorts.