Method and apparatus for checking the plausibility of the functionality of a crankcase ventilation system

1. A method for checking the plausibility of the functionality of a crankcase ventilation system of an internal combustion engine, wherein crankcase ventilation system has a crankcase, an intake tract equipped with an intake manifold, and a connecting line arranged between the crankcase and the intake manifold, the method comprising:

detecting an occurrence of a negative load change;

in response, comparing a measured intake manifold pressure with a modelled intake manifold pressure using acquired operating variables of the internal combustion engine and of a crankcase model;

wherein the connecting line pneumatically connects a free volume of the crankcase to the intake tract at a point downstream of a throttle valve in the intake tract;

comparing the measured intake manifold pressure to the measured ambient pressure;

if the measured intake manifold pressure is higher than the ambient pressure, waiting until a negative load change occurs;

upon detecting an occurrence of a negative load change, comparing the measured intake manifold pressure to the measured ambient pressure,

activating a diagnostic window if the measured intake manifold pressure undershoots the measured ambient pressure;

calculating a difference or an integral of the difference between the measured intake manifold pressure and the modelled intake manifold pressure within the diagnostic window;

comparing the determined difference or the integral of the difference to a predefined threshold value; and

if the determined difference or the integral of the difference is greater than the threshold value, detecting whether the connecting line arranged between the crankcase and the intake manifold has a blockage or drops out.

2. The method as claimed in claim 1 , further comprising adapting operation of the internal combustion engine in response to detecting the connecting line arranged between the crankcase and the intake manifold has a blockage or drops out.

3. The method as claimed in claim 2 , wherein adapting operation of the internal combustion engine includes making an entry is made in a fault register or deactivating a crankcase function or displaying a fault.

4. An internal combustion engine comprising:

a crankcase ventilation system;

a crankcase;

an intake tract equipped with an intake manifold;

a connecting line arranged between the crankcase and the intake manifold, wherein the connecting line pneumatically connects a free volume of the crankcase to the intake tract at a point downstream of a throttle valve in the intake tract; and

a control apparatus having a processor and a memory storing instructions, when loaded and execute by the processor, configure the processor to:

detect an occurrence of a negative load change;

in response, compare a measured intake manifold pressure with a modelled intake manifold pressure using acquired operating variables of the internal combustion engine and of a crankcase model;

comparing the measured intake manifold pressure to the measured ambient pressure;

if the measured intake manifold pressure is higher than the ambient pressure, waiting until a negative load change occurs;

upon detecting an occurrence of a negative load change, comparing the measured intake manifold pressure to the measured ambient pressure,

activating a diagnostic window if the measured intake manifold pressure undershoots the measured ambient pressure;

calculating a difference or an integral of the difference between the measured intake manifold pressure and the modelled intake manifold pressure within the diagnostic window;

comparing the determined difference or the integral of the difference to a predefined threshold value; and

if the determined difference or the integral of the difference is greater than the threshold value, detecting whether the connecting line arranged between the crankcase and the intake manifold has a blockage or drops out.