Systems and methods for monitoring crankcase ventilation system integrity are disclosed. In one example approach, a method comprises indicating a crankcase ventilation system degradation based on a lower vacuum than expected downstream of a PCV breather tube. For example, indicating a crankcase ventilation system degradation based on a lower vacuum than expected downstream of a PCV breather tube may include indicating a crankcase ventilation system degradation based on an absolute pressure sensor measurement relative to a gauge pressure sensor measurement.