Detection of crankcase integrity violations

Abstract

Method (300) for monitoring a crankcase ventilation system (16) for an engine (10), comprising the following: the indication of an impairment of the crankcase ventilation system (16) based on a lower than expected vacuum in a crankcase (28), wherein the lower than expected vacuum is relative to atmospheric pressure, wherein the crankcase ventilation system (16) comprises two air pressure sensors (51), a compressor inlet pressure sensor (58) and a pressure sensor (61), wherein the air pressure sensor (51) is arranged in an engine intake (12) upstream of an air filter (54), wherein the compressor inlet pressure sensor (58) is arranged upstream of a compressor (50) and downstream of a coupling (208) of a fresh air tube (74) with the engine intake (12), and wherein the pressure sensor (61) is arranged in a crankcase ventilation tube (74), wherein the first of the two, consisting of the air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61), is an absolute pressure sensor that measures an absolute pressure relative to a perfect vacuum, wherein the second, consisting of the air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61), is a relative pressure sensor that measures a relative pressure relative to atmospheric pressure, and wherein a control unit (48) determines the vacuum based on an absolute pressure measurement relative to a relative pressure measurement using the two from the air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61).

Description

[0001] Engines may include crankcase forced ventilation systems, hereinafter also referred to as crankcase ventilation systems (PCV), to vent gases from the crankcase and into an engine intake manifold to ensure a continuous evacuation of gases from inside the crankcase in order to reduce the impairment of various engine components within the crankcase.

[0002] Under certain conditions, crankcase ventilation systems can be monitored to identify damage to the system. For example, a fresh air hose (a vent tube "CVT") may be disconnected, an oil filler cap may be missing or loose, a dipstick may be protruding, and / or other seals in the crankcase ventilation system may be compromised, leading to damage to various components enclosed within the crankcase.

[0003] Diagnostic blow-through methods can be used to monitor the integrity of a crankcase ventilation system. For example, a pressure sensor can be used in the crankcase, and a valve in a PCV fresh air hose can be opened so that pressure or vacuum changes in the crankcase can be felt to determine if there is a leak in the system.

[0004] Other approaches may use multiple absolute sensors, e.g., an air pressure sensor (BP), a compressor inlet pressure sensor (CIP), a throttle inlet pressure sensor (TIP), a manifold air pressure sensor (MAP), and / or a pressure sensor in a crankcase ventilation hose, etc., in combination to monitor the integrity of a crankcase ventilation system.

[0005] However, the inventors of the present system recognized that such approaches to monitoring systems can add additional equipment, such as additional sensors and valves, consequently increasing the cost and complexity of a crankcase ventilation monitoring system. For example, a compressor inlet and a crankcase ventilation pipe may, under certain conditions, indicate essentially the same pressure; therefore, including sensors in both the PCV ventilation pipe and the compressor inlet may not be necessary when used in conjunction with an air pressure sensor during crankcase ventilation system diagnostic routines.

[0006] US 2011 / 0197864A1 discloses a generic method for monitoring a tank venting system and a crankcase venting system of an internal combustion engine.

[0007] DE 10 2010 040 900 A1, US 2010 / 0 147 270 A1, US 5 792 949 A and DE 100 26 492 A1 disclose further generic methods and devices for diagnosing a crankcase ventilation system.

[0008] The objective technical problem to be solved can be seen as eliminating or at least reducing the disadvantages of the prior art. According to the invention, this problem is solved by the subject matter of the independent claims.

[0009] Consequently, one approach to addressing these problems, at least in part, provides a method for monitoring the integrity of a crankcase ventilation system. This method involves indicating a crankcase ventilation system impairment based on a lower-than-expected vacuum downstream in a crankcase ventilation tube or in the main engine air duct to which the crankcase ventilation tube is attached. Indicating a crankcase ventilation system impairment based on a lower-than-expected vacuum downstream of a crankcase ventilation tube includes indicating a crankcase ventilation system impairment based on an absolute pressure sensor reading relative to a relative pressure sensor reading.

[0010] This approach can potentially reduce the number of sensors and valves used in a crankcase ventilation monitoring system, leading to a reduction in both cost and complexity. Furthermore, it allows the crankcase ventilation system to remain active during diagnostic procedures.

[0011] It should be understood that the summary above is provided to introduce, in simplified form, a selection of concepts that are further described in the full description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the full description. Furthermore, the claimed subject matter is not limited to implementations that resolve any disadvantages identified above or in any part of this disclosure. Fig. Figure 1 shows a partial view of the engine after the revelation. Fig. Figure 2 shows exemplary embodiments of crankcase ventilation system monitoring sensors according to the disclosure. Fig. Figure 3 shows an exemplary procedure for an engine according to the revelation.

[0012] The following description concerns systems and methods for monitoring the integrity of a crankcase ventilation system in an engine crankcase ventilation system, such as the system of Fig. 1. Various sensor configurations are possible, such as in Fig. 2 shown, can be used to monitor a crankcase ventilation system to detect damage to the system while using a reduced number of sensors. For example, as shown in Fig. Figure 3 shows that the comparison of two sensor readings can be used to detect violations of the crankcase ventilation system, such as a disconnection of the PCV fresh air hose.

[0013] With reference to Fig. Figure 1 shows an exemplary system configuration of a multi-cylinder internal combustion engine, generally depicted at 10, which may be included in a motor vehicle's drive system. The engine 10 can be controlled, at least partially, by a control system that includes a control unit 48 and by input from a driver 132 via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP.

[0014] The engine 10 can include a lower section of the engine block, generally shown at 26, which includes a crankcase 28 enclosing a crankshaft 30, with an oil pan 32 located below the crankshaft. An oil filler channel 29 can be arranged in the crankcase 28 so that oil can be supplied to the oil pan 32. The oil filler channel 29 can include an oil cap 33 to seal the oil channel 29 when the engine is running. A dipstick tube 37 can also be arranged in the crankcase 28 and can include a dipstick 35 for measuring an oil level in the oil pan 32. Furthermore, the crankcase 28 can include several other openings for servicing components within the crankcase 28. These openings in the crankcase 28 can be kept closed during engine operation, allowing a crankcase ventilation system (described below) to operate during engine operation.

[0015] The upper section of the engine block 26 can include a combustion chamber (i.e., a cylinder) 34. The combustion chamber 34 can include combustion chamber walls 36, in which a piston 38 is arranged. The piston 38 can be coupled to the crankshaft 30 so that the reciprocating motion of the piston is converted into a rotary motion of the crankshaft. The combustion chamber 34 can receive fuel from fuel injectors 40 and intake air from an intake manifold 42 located downstream of a throttle 44. The engine block 26 can also include an engine coolant temperature (ECT) sensor 46, which provides input to an engine control unit 48 (described in more detail below).

[0016] A throttle 44 can be arranged in the engine intake to control the airflow entering the intake manifold 42, and a compressor 50 can be located upstream of it, followed, for example, by an intercooler 52. An air filter 54 can be arranged upstream of the compressor 50 and can filter fresh air entering an intake duct 56.

[0017] Combustion exhaust gases exit the combustion chamber 34 via an exhaust channel 60 located upstream of a turbine 62. An exhaust gas sensor 64 can be arranged upstream of the turbine 62 along the exhaust channel 60. The turbine 62 can be equipped with a boost pressure control valve that bypasses it. The sensor 64 can be a suitable sensor for providing an indication of the exhaust-air-fuel ratio, such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a dual-state oxygen sensor or EGO, a HEGO (heated EGO), or an NO sensor. x -, HC, or CO sensor. The exhaust gas sensor 64 can be connected to the control unit 48.

[0018] In the example of Fig. 1 is a positive crankcase ventilation (PCV) system 16 coupled to the engine intake so that gases in the crankcase can be vented from the crankcase in a controlled manner. The crankcase ventilation system 16 draws air into the crankcase 28 via a vent hole or vent tube 74. The vent tube 74 can be coupled upstream of the compressor 50 to a fresh air intake duct 12. In some examples, the vent tube can be coupled to the air filter 54. In other examples, the vent tube can be coupled downstream of the air filter 54 to the intake 12.

[0019] The crankcase ventilation system vents air from the crankcase and into the intake manifold 42 via a line 76, which in some examples may include a one-way PCV valve 78, to ensure continuous evacuation of gases from inside the crankcase 28 before it connects to the intake manifold 42. However, in other examples, the PCV line 76 may not include a one-way PCV valve. As in the example of Fig. As shown in Figure 1, the PCV line 76 can include a unidirectional oil separator 80 that filters oil from vapors exiting the crankcase 28 before they re-enter the intake system 12. Another oil separator 81 can be arranged in the line 74 to filter oil from vapors exiting the crankcase 28. In some examples, the PCV line 76 can also include a vacuum sensor coupled to the PCV system. In some examples, the gas flow in the line 74 can be bidirectional, from the crankcase 28 to the intake 12 and / or from the intake 12 to the crankcase 28. Furthermore, in some examples, during certain engine operating conditions, e.g. in turbocharger applications, gas can flow through line 76 in both directions, from the crankcase 28 to the intake 42 and / or from the intake 42 to the crankcase 28.

[0020] While the engine is running under light load and moderate throttle opening, the intake manifold pressure may be lower than the crankcase pressure. The lower intake manifold pressure draws fresh air towards it, which draws air from the crankcase ventilation tube 74 through the crankcase (where it dilutes and mixes with combustion gases), through the PCV valve, and into the intake manifold.

[0021] The control unit 48 is located in Fig. Figure 1 shows a microcomputer comprising a microprocessor unit 108, input / output ports 110, an electronic storage medium for executable programs and calibration values ​​(shown in this particular example as a solid-state memory chip 112), random-access memory 114, battery-powered memory 116, and a data bus. The control unit 48 receives various signals from sensors coupled to the engine 10: the engine coolant temperature (ECT) from the temperature sensor 46, the EGR pressure from a vacuum sensor 72, the exhaust-air-fuel ratio from the exhaust gas sensor 64, and other PCV diagnostic sensors described below. The solid-state memory 112 of the storage medium can be programmed with computer-readable data representing instructions that can be executed by the processor 108 to perform the procedures described below, as well as other variations considered but not specifically listed.

[0022] As noted above, under certain conditions, crankcase ventilation systems can be monitored via multiple sensors to identify damage within the system. For example, a crankcase ventilation tube may become disconnected, an oil filler cap may be missing or loose, a dipstick may be protruding, and / or other seals within the crankcase ventilation system may be compromised, potentially leading to damage to various components enclosed within the crankcase.

[0023] Diagnostic blow-through approaches can be used to monitor the integrity of a crankcase ventilation system. For example, a pressure sensor 63 can optionally be used in the crankcase, and a valve (not shown) in the crankcase vent pipe 74 can be opened so that pressure or vacuum changes in the crankcase can be sensed to determine if there is a breach in the venting system. However, as noted above, with such blow-through approaches, a valve in the fresh air pipe 74 may be closed during part of the monitoring routine, preventing crankcase gases from being expelled and potentially leading to component degradation.

[0024] In other approaches, multiple absolute sensors, e.g., an air pressure sensor (BP) 51, a compressor inlet pressure sensor (CIP) 58, and / or a pressure sensor 61 in the crankcase ventilation tube 74, can be used to monitor the integrity of a crankcase ventilation system. For example, in some approaches, an air pressure sensor 51, a compressor inlet sensor 58, and a pressure sensor 61 in the PCV fresh air tube 74 can all be used to monitor the integrity of a crankcase ventilation system. However, using all of these sensors to monitor the integrity of a crankcase ventilation system may be unnecessary and may increase the costs associated with including all of them.For example, a compressor inlet and a crankcase ventilation tube may indicate essentially the same pressure under certain conditions; consequently, including sensors in both the PCV ventilation tube and the compressor inlet may not be necessary when used in combination with an air pressure sensor during crankcase ventilation system diagnostic routines.

[0025] Consequently, instead of using a combination of the BP sensor 51, the CIP sensor 58 and the pressure sensor 61, a monitoring system can use two sensors, an absolute pressure sensor and a relative pressure sensor, in various configurations, such as the one described below. Fig. Use as shown in section 2.

[0026] For example, it shows Fig. 2 A first embodiment 202 of a sensor configuration of a crankcase ventilation monitoring system. This embodiment 202 includes a pressure-pressure (BP) sensor 51 located in the engine intake 12 upstream of the air filter 54 and a coupling 208 of the crankcase ventilation tube 74 with the intake 12. However, in other embodiments, the BP sensor 51 can be located at any position suitable for measuring air pressure. For example, the BP sensor can be located in the intake 12 or within the coupling 208 of the ventilation tube 74 with the intake 12.

[0027] Fig. Figure 2 shows that the crankcase ventilation tube 74 is coupled to the clean air side of the air filter 54; however, in other examples, the ventilation tube 74 can be coupled downstream of the air filter 54 to the intake 12. For example, the ventilation tube 74 can be coupled downstream of the air filter 54 and upstream of the compressor 50 to the intake 12.

[0028] The embodiment 202 also includes a CIP sensor 58, which is arranged upstream of the compressor 50 and downstream of the coupling 208 of the fresh air tube 74 with the intake 12. In some examples, the CIP sensor can be arranged in an inlet of the compressor 50 so that the air pressure entering the compressor 50 can be measured.

[0029] In embodiment 202, one of the BP sensor 51 and the CIP sensor 58 can be an absolute pressure sensor configured to measure pressure relative to a perfect vacuum, and the other of the BP sensor 51 and the CIP sensor 58 can be a differential or relative pressure sensor configured to measure pressure relative to atmospheric pressure. For example, the BP sensor 51 can be an absolute pressure sensor, and the CIP sensor 58 can be a relative pressure sensor. Alternatively, the BP sensor 51 can be a relative pressure sensor, and the CIP sensor 58 can be an absolute pressure sensor.

[0030] As noted above, under certain conditions, such as during high engine airflow rates, a pressure gauge located upstream of the compressor 50 and downstream of the coupling 208 of the crankcase ventilation tube 74 with the intake 12, e.g., at a compressor inlet, can be essentially the same as a pressure gauge in the crankcase ventilation tube 74. Consequently, in some examples, as shown in embodiment 204, instead of enclosing a CIP sensor 58, a pressure sensor 61 can be arranged in the crankcase ventilation tube 74 and used together with the BP sensor 51 to monitor the crankcase ventilation system.

[0031] In embodiment 204, one of the BP sensor 51 and the vent tube pressure sensor 61 can be an absolute pressure sensor configured to measure pressure relative to a perfect vacuum, and the other of the BP sensor 51 and the vent tube pressure sensor 61 can be a differential or relative pressure sensor configured to measure pressure relative to atmospheric pressure. For example, the BP sensor 51 can be an absolute pressure sensor, and the vent tube pressure sensor 61 can be a relative pressure sensor. Alternatively, the BP sensor 51 can be a relative pressure sensor, and the vent tube pressure sensor 61 can be an absolute pressure sensor.

[0032] As another example, under certain conditions, such as during high engine airflow rates, a pressure reading in the crankcase ventilation tube 74 can be essentially the same as a pressure reading measured by the BP sensor 51. Consequently, in some examples, as shown in embodiment 206, instead of enclosing a BP sensor 51, a pressure sensor 61 can be arranged in the crankcase ventilation tube 74 and used together with the CIP sensor 58 to monitor the crankcase ventilation system.

[0033] In embodiment 206, one of the CIP sensor 58 and the vent tube pressure sensor 61 can be an absolute pressure sensor configured to measure pressure relative to a perfect vacuum, and the other of the CIP sensor 58 and the vent tube pressure sensor 61 can be a differential or relative pressure sensor configured to measure pressure relative to atmospheric pressure. For example, the CIP sensor 58 can be an absolute pressure sensor, and the vent tube pressure sensor 61 can be a relative pressure sensor. Alternatively, the CIP sensor 58 can be a relative pressure sensor, and the vent tube pressure sensor 61 can be an absolute pressure sensor.

[0034] Fig. Figure 3 shows an exemplary method 300 for monitoring a crankcase ventilation system and detecting injuries in the crankcase ventilation system 16 using one of the methods described in Fig.2 sensor configurations shown. For example, a malfunction of the crankcase ventilation system can be indicated based on an absolute pressure measurement relative to a relative pressure measurement, as described below.

[0035] In procedure 302, method 300 includes determining whether activation conditions are met. For example, the activation conditions may include an engine operating condition of high intake airflow, such as a turbocharger spooling up, an engine speed greater than a threshold, etc. For example, the monitoring routine may be initiated in response to an operator-activated accelerator pedal position, such as in response to the driver pressing the accelerator pedal.

[0036] If the entry conditions are met at 302, procedure 300 proceeds to 304. At 304, procedure 300 includes determining a pressure using an absolute pressure sensor. For example, atmospheric pressure (BP) can be determined based on an BP absolute sensor, such as sensor 51. In other examples, depending on the sensor configuration of the monitoring system, the pressure can be determined by a CIP absolute sensor or an absolute pressure sensor 61 in the vent tube 74.

[0037] In 306, procedure 300 includes determining a pressure across a relative pressure sensor. For example, a compressor inlet pressure (CIP) can be determined based on a CIP relative sensor, such as sensor 58. In other examples, depending on the sensor configuration of the monitoring system, the pressure can be determined by a BP relative sensor or a relative pressure sensor in the vent tube 74.

[0038] In 308, method 300 includes comparing the absolute sensor pressure and the relative sensor pressure. For example, an air pressure reading from the BP sensor 51 can be compared with a compressor inlet pressure reading from the CIP sensor 58, e.g., in embodiment 202. In other examples, a pressure reading from the vent tube pressure sensor 61 can be compared with an air pressure reading from the BP sensor 51, e.g., in embodiment 204. In still other examples, a pressure reading from the vent tube pressure sensor 61 can be compared with a compressor inlet pressure reading from the CIP sensor 58, e.g., in embodiment 206.

[0039] In 310, procedure 300 includes indicating a crankcase ventilation system impairment based on a comparison of the absolute sensor pressure and the relative sensor pressure, e.g., based on a comparison of the BP pressure and the CIP pressure. For example, a crankcase ventilation system impairment, such as a breach in the crankcase ventilation system, may be indicated if the absolute pressure sensor reading is substantially equal to the relative pressure sensor reading. Furthermore, in some examples, a crankcase ventilation system impairment may not be indicated if the absolute pressure sensor reading is not substantially equal to the relative pressure sensor reading.

[0040] Specifically, if there is a fault in the crankcase ventilation system, for example, if the vent pipe 74 has been disconnected from the intake 12, the oil cap 33 is missing or loose, or the dipstick 35 is out, then, for example, during engine operating conditions of high airflow, a pressure reading upstream of the clutch 208 may be essentially the same as a pressure reading at an inlet of the compressor 50. As another example, if there is a fault in the crankcase ventilation system, then a pressure reading in the vent pipe 74 may be essentially the same as an air pressure reading, e.g., via the BP sensor 51. As yet another example, if there is a fault in the crankcase ventilation system, then a pressure reading in the vent pipe 74 may be essentially the same as a pressure reading at an inlet of the compressor 50, e.g., via the CIP sensor 58.

[0041] It should be noted that the exemplary control and estimation routines included herein can be used with various system configurations. The specific routines described herein can embody one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various illustrated steps, operations, or functions in the illustrated sequence can be executed in parallel or, in some cases, omitted. Likewise, the order of processing is not necessarily required to achieve the features and benefits described herein but is provided for ease of illustration and description. One or more of the illustrated steps, functions, or operations may be executed repeatedly, depending on the particular strategy used.Furthermore, the described operations, functions and / or steps can graphically represent a code that is to be programmed into the computer-readable storage medium in the engine control system.

[0042] Furthermore, it should be understood that the systems and methods described herein are exemplary and that these specific embodiments are not to be considered limiting, as numerous variations are provided for. Accordingly, the present disclosure includes all novel and non-obvious combinations of the various systems and configurations disclosed herein, as well as all and any equivalents thereof.

Claims

[1] Method (300) for monitoring a crankcase ventilation system (16) for an engine (10), comprising the following: the indication of an impairment of the crankcase ventilation system (16) based on a lower than expected vacuum in a crankcase (28), wherein the lower than expected vacuum is relative to atmospheric pressure, wherein the crankcase ventilation system (16) comprises two air pressure sensors (51), a compressor inlet pressure sensor (58) and a pressure sensor (61), wherein the air pressure sensor (51) is arranged in an engine intake (12) upstream of an air filter (54), wherein the compressor inlet pressure sensor (58) is arranged upstream of a compressor (50) and downstream of a coupling (208) of a fresh air tube (74) with the engine intake (12), and wherein the pressure sensor (61) is arranged in a crankcase ventilation tube (74), wherein the first of the two, consisting of the air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61), is an absolute pressure sensor that measures an absolute pressure relative to a perfect vacuum, wherein the second, consisting of the air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61), is a relative pressure sensor that measures a relative pressure relative to atmospheric pressure, and wherein a control unit (48) determines the vacuum based on an absolute pressure measurement relative to a relative pressure measurement using the two from the air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61). [2] Method (300) according to claim 1, wherein the absolute pressure sensor is the air pressure sensor (51) upstream of the air filter (54) and the relative pressure sensor is the compressor inlet pressure sensor (58). [3] Method (300) according to claim 1, wherein the absolute pressure sensor is the air pressure sensor (51) upstream of the air filter (54) and the relative pressure sensor is the pressure sensor (61) arranged in the crankcase ventilation tube (74). [4] Method (300) according to claim 1, wherein the absolute pressure sensor is the compressor inlet pressure sensor (58) and the relative pressure sensor is the air pressure sensor (51) upstream of the air filter (54). [5] Method (300) according to claim 1, wherein the absolute pressure sensor is the pressure sensor (61) arranged in a crankcase ventilation tube (74) and the relative pressure sensor is the air pressure sensor (51) upstream of the air filter (54). [6] Method (300) according to claim 1, wherein the absolute pressure sensor is the compressor inlet pressure sensor (58) and the relative pressure sensor is the pressure sensor (61) arranged in the crankcase vent tube (74). [7] Method (300) according to claim 2, wherein the absolute pressure sensor is the pressure sensor (61) arranged in the crankcase vent tube (74) and the relative pressure sensor is the compressor inlet pressure sensor (58). [8] Method (300) according to claim 1, wherein an impairment of the crankcase ventilation system (16) is indicated when the absolute pressure sensor measurement is substantially equal to the relative pressure sensor measurement. [9] Method (300) according to claim 1, wherein the absolute pressure sensor measurement and the relative pressure sensor measurement are measured during an engine operating condition of high intake air flow. [10] Method (300) according to claim 1, wherein indicating an impairment of the crankcase ventilation system (16) includes indicating a violation in the crankcase ventilation system (16). [11] Method (300) for monitoring a crankcase ventilation system (16) for an engine (10), comprising the following: indicating an impairment of the crankcase ventilation system (16) based on relative pressure sensor readings from only two of an air pressure sensor (51) upstream of an air filter (54), a compressor inlet pressure sensor (58) and a pressure sensor (61) arranged in a crankcase ventilation tube (74), wherein the compressor inlet pressure sensor (58) is arranged upstream of a compressor (50) and downstream of a coupling (208) of a fresh air tube (74) with the engine intake (12), and wherein the pressure sensor (61) is arranged in a crankcase ventilation tube (74), wherein the two air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61) are relative pressure sensors that measure a relative pressure relative to atmospheric pressure, and wherein a control unit (48) determines the impairment of the crankcase ventilation system (16) based on relative pressure measurements using the two air pressure sensor (51), the compressor inlet pressure sensor (58) and the pressure sensor (61). [12] Method (300) according to claim 11, wherein an impairment of the crankcase ventilation system (16) is indicated when the sensor readings of only two of the air pressure sensor (51) upstream of the air filter (54), the compressor inlet pressure sensor (58) and the pressure sensor (61) arranged in the crankcase ventilation tube (74) are substantially the same. [13] Method (300) according to claim 11, wherein an impairment of the crankcase ventilation system (16) is not indicated if the sensor readings of only two of the air pressure sensor (51) upstream of the air filter (54), the compressor inlet pressure sensor (58) and the pressure sensor (61) arranged in the crankcase ventilation tube (74) are not substantially the same. [14] Method (300) according to claim 11, wherein the sensor readings of only two of the air pressure sensor (51) upstream of the air filter (54), the compressor inlet pressure sensor (58) and the pressure sensor (61) arranged in the crankcase ventilation tube (74) are measured during an engine operating condition of high intake air flow. [15] Method (300) according to claim 11, wherein indicating an impairment of the crankcase ventilation system (16) includes indicating a violation in the crankcase ventilation system (16). [16] Method (300) for an engine (10) with a crankcase forced ventilation system, wherein the method (300) comprises: the indication of a malfunction of the crankcase ventilation system (16) based on an air pressure relative to a compressor inlet pressure, during an engine operating condition of high air velocity, wherein the air pressure is measured via an air pressure sensor (51) arranged in an intake of the engine (10) upstream of a crankcase ventilation tube coupling (208) with the engine intake (12) and the compressor inlet pressure is measured via a pressure sensor (61) arranged in the crankcase ventilation tube coupling (208) with the engine intake (12) and wherein an impairment of the crankcase ventilation system (16) is indicated when the air pressure is substantially equal to the compressor inlet pressure.

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