MXPA01005670A - System and method for detecting engine malfunction based on crankcase pressure - Google Patents

Abstract

A new system and method for detecting engine malfunctions based on crankcase pressure (150) include determining a reference value indicative of current engine operating conditions (152) and using the reference value to determine a crankcase pressure limit (160) which varies as a function of the reference value. The sensed crankcase pressure is compared to the limit (162) to determine when a fault condition exists. The reference value is preferably a function of engine speed (154) and requested engine torque (156) and includes a second order term multiplied by a calibratable constant which controls sensitivity of the fault determination. The sensitivity may be adjusted to provide equally detectable faults across all engine speeds and loads, to be more sensitive to faults occurring at higher engine speeds, or to be more sensitive to faults occurring at higher engine loads. The system and method control the engine based on the determination of an engine fault. Subsequent control may include alerting the vehicle operator, reducing available engine torque (168), stopping the engine (170) and/or logging a fault (174) for subsequent service or maintenance. Early cylinder/piston fault detection provides more time for the vehicle operator and/or the engine controller to take remedial actions to prevent more serious engine damage.

Description

SYSTEM AND METHOD FOR DETECTING MALFUNCTION OF THE ENGINE BASED ON PRESSURE OF THE SUMP TECHNICAL FIELD The present invention relates to a system and method for detecting a malfunction of the engine in an internal combustion engine using the crankcase pressure.

PREVIOUS TECHNIQUE In the control of combustion engines, conventional practice uses electronic control units that have volatile and non-volatile memory, conductive input and output circuits and a processor capable of executing a set of stored instructions, to control the various functions of the motor and its associated systems. A particular electronic control unit communicates with various sensors, actuators and other electronic control units necessary to control the different functions which may include various aspects of diagnosis of engine malfunction, fuel supply, transmission control and many others. The diagnosis of malfunction of internal combustion engines is a common issue. This is due to the desire to detect engine failures or malfunctions before they occur, or as soon as possible after they occur, to provide an opportunity to take action to avoid severe engine damage. The crankcase pressure has been used to detect various engine malfunctions in relation to the pistons. The method is to use a pressure safety switch which provides a signal when the crankcase pressure exceeds a predetermined threshold. This approach requires a pressure safety switch selected based on the particular application or a family of engines that exhibit similar crankcase pressures during operation. A crankcase pressure exceeding the predetermined threshold results in the generation of the safety switch of a signal that can be used by the electronic control unit to indicate a failure. The electronic control unit may then execute the appropriate action depending on the particular application, which may include generating a warning message or an indicator light, or turning off the engine for example. Another method of detecting a malfunction of the engine based on the crankcase pressure uses a pressure sensor that provides a continuously variable signal representing the current crankcase pressure. The electronic control unit periodically samples the signal generated by the pressure sensor and compares it with a predetermined crankcase pressure limit. The pressure limit is generally a value that is determined based on the expected crankcase pressure at the expected maximum engine speed and load (or power). This method allows the use of an individual crankcase pressure sensor for applications since the limit value can be calibrated for each motor or motor family and stored in the electronic control unit. While this strategy is able to detect several malfunctions in relation to the piston or cylinder at the maximum load speed, it is insufficient to detect impending faults at low speeds and loads. In addition, it is desirable to detect impending faults or failures as soon as possible to provide the electronic control unit or vehicle operator with sufficient time to take remedial action to avoid a catastrophic failure.

DESCRIPTION OF THE INVENTION Therefore, it is an object of the present invention to provide a method and system for the detection of improved engine malfunction based on the crankcase pressure of the engine. Another object of the present invention is to provide a system and method for detecting a malfunction of the motor having a selectable or tunable sensitivity for various applications. A further object of the present invention is to provide a system and method for detect engine malfunctions related to the piston / cylinder at low speeds and engine loads. Another object of the present invention is to provide a system and method for detecting an engine failure having an equal detection capacity of excessive crankcase pressure at all speeds and loads. A further object of the present invention is to provide a system and method for motor protection that operates while the motor is operating at less than the maximum power. A further object of the present invention is to provide a system and method for motor protection capable of detecting a faulty piston condition immediately after the motor is started. In carrying out the above object and other objects and features of the present invention, a method for detecting malfunctions of the engine is provided. The method includes detecting the crankcase pressure, determining a current value for at least one operating parameter of an engine and comparing the crankcase pressure with a limit that varies as a function of at least one engine operating parameter. The method further comprises providing an indication that the crankcase pressure has exceeded the crankcase pressure limit and may also include engine control based on the indication. In one embodiment, an indexing value is determined based on the parameters or operating parameters of the engine and is used to access a search table that contains the crankcase pressure limit values.

Preferably, the index value is a function of the motor speed and the required torque. Of course, said at least one engine operating parameter may be any one or more of a variety of engine operating parameters that are measured, detected, calculated or inferred, including engine speed, actual torque or required, oil temperature, oil pressure, fuel temperature, coolant temperature and the like. In carrying out the above objects and other objects, features and advantages of the invention, a computer-readable storage medium is provided. The computer-readable storage medium has the information stored therein that represents instructions executable by a computer to improve the detection of motor malfunction. The computer-readable storage medium includes instructions for determining the crankcase pressure limit based on at least one operating parameter of the engine. The computer-readable storage medium also includes instructions for comparing a detected crankcase pressure to the determined limit and generating a signal when the detected crankcase pressure exceeds the limit. A system for providing improved failure detection based on engine crankcase pressure includes a crankcase pressure sensor to provide a continuously variable signal indicative of crankcase pressure in communication with an electronic control unit to control a combustion engine internal The system also includes at least one additional sensor that provides a signal indicative of an engine operating parameter. The electronic control unit includes the control logic to determine a value indicative of the crankcase pressure based on a signal provided by the crankcase pressure sensor. The electronic control unit also includes in the control logic to determine a reference value indicative of the operating conditions of the motor based on the signals provided by at least one additional sensor. The electronic control unit uses the reference value to determine a current limit for the crankcase pressure and compares the crankcase pressure value with the limit. If the crankcase pressure value exceeds the limit value, the control logic generates a corresponding fault signal or code. The fault code may be registered for future reference by the service personnel and used by the electronic control unit for subsequent processing which may include turning on a service indicator, reducing the available motor power and / or the engine shutdown. The advantages that accumulate for the present invention are varied. For example, the present invention facilitates the detection of faults insofar as the motor is operating at less than the maximum power. The present invention will detect a piston condition with failure almost immediately after the engine is restarted. The present invention provides a selectable failure detection strategy which can be adjusted or released to change its sensitivity based on the particular application. The above object and other objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention, when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of one embodiment of a motor malfunction detection system based on the crankcase pressure according to the present invention; Figure 2 is a graph illustrating the normal operation crankcase pressure as a function of a parameter of the engine operation together with an associated crankcase pressure failure limit having set sensitivity for a lower tolerance at higher engine speeds; Figure 3 is a graph illustrating the normal operation crankcase pressure as a function of an engine operating parameter including a crankcase pressure limit when the malfunction detection is more sensitive at a higher position of the accelerator pedal or engine load; Figure 4 is a graph illustrating normal operating crankcase pressure as a function of an engine operating parameter that includes a crankcase pressure limit when detecting equally sensitive malfunction through engine speeds and loads; and Figure 5 is a block diagram illustrating the operation of a system or method according to the present invention for detecting a malfunction of the engine based on the crankcase pressure.

BEST WAY TO CARRY OUT THE INVENTION Referring now to Figure 1, there is shown a system for detecting a malfunction of the engine based on the pressure of the crankcase according to the present invention. The system, indicated generally by the reference number 10, includes a motor 12 having a plurality of cylinders with a representative cylinder indicated generally by the reference numeral 14. In a preferred embodiment, the motor 12 is an internal combustion engine of compression-ignition of multiple cylinders, such as for example four, six, eight, twelve, sixteen, or twenty-four cylinders of diesel engine, for example. Each cylinder 14 includes a piston 16 operatively associated with the crankcase 18 by means of a connecting rod 20 as is well known in the art. An electronic injector 22 has a solenoid 24 which is operatively associated with a crankshaft 26 by means of a rocker arm 28 to control the supply of fuel to the engine 12. The piston 16 includes piston rings 30? to separate the combustion chamber 32 from the opposite side of the piston / cylinder 34 which is in fluid communication with the crankcase 36 in an open crankcase ventilation arrangement. The system 10 preferably includes a crankcase pressure sensor that provides a continuously variable signal indicative of pressure within the crankcase 36. In one embodiment of the present invention, the crankcase pressure sensor 38 is a gauge pressure transducer vented to the atmosphere with a range of +/- 5 volts corresponding to a pressure of +/- 1 psig (0.0703 kg / cm2 gauge). The system 10 also preferably includes a motor speed sensor 39 which detects the rotational speed and / or the position of the crankcase 18. The system 10 further includes an accelerator / accelerator pedal sensor 40 for determining the position of the accelerator pedal. Accelerator 42 indicating the torque of the engine requested by the vehicle operator. The system 10 may also include several more sensors 44 to generate signals indicative of the corresponding operating conditions or parameters of the engine 12 or the vehicle (not shown). The sensors 44 may include appropriate sensors to provide signals indicative of boost pressure, air temperature, oil temperature, oil pressure, oil level, fuel pressure, vehicle speed, and coolant level, in addition to the switches appropriate ones connected to an operator interface to select various optional motor operation modes including a stopped motor cancellation, cruise control selection and setting and the like. The parameters of the operation of the engine and / or vehicle or conditions can also be calculated, determined or inferred based on one or more of the detected parameters or operating conditions indicated by the sensors 44. For example, the requested torque can be inferred or determined based on a signal from the accelerator pedal sensor 40. Similarly, the power of the motor can be determined based on the speed of the motor and the torque required. Other engine operating parameters or reference values can be determined in a similar manner as will be appreciated by someone skilled in the art. The sensors 44 are in electrical communication with a controller 46 via input ports and / or conditioning circuits 48. In a preferred embodiment, the controller 46 is the DDEC controller available from the Detroit Diesel Corporation, Detroit, Michigan. Various other features of this controller are described in detail in U.S. Patent Nos. 5,477,827 and 5,445,128, the descriptions of which are incorporated herein by reference in their entirety. The controller 46 preferably includes a microprocessor 50 in communication with various computer readable storage means 52 through data and control headers 54. The computer readable storage means 52 can include any of a number of known devices that function as a read-only memory (ROM) 56, random access memory (RAM) 58, retention memory (KAM) 60, and the like. The computer readable storage medium can be implemented by any of a number of known physical devices capable of storing data representing executable instructions by means of a computer such as controller 46. The devices may include, but not be limited to, PROM, EPROM, EEPROM, immediate memory and similar in addition to magnetic, optical and combinations capable of storing data temporarily or permanently. The computer readable storage medium 52 includes data representing program instructions (software), calibrations, operational variables and the like used with the associated hardware to effect control of various vehicle systems and subsystems, such as the engine 12. controller 46 receives signals from sensors 44 by means of input ports 48 and generates output signals that can be provided to various actuators 62 and / or components by means of output ports 64. The signals can also be provided to a device of display 66 which may include various indicators such as lights 68 to communicate the information regarding the operation of the system to the vehicle operator. Of course, alphanumeric, audio, video or other displays or indicators may be used if desired. With continued reference to Figure 1, the control logic implemented by the controller 46 and the hardware and / or software determine whether the current crankcase pressure as indicated by the pressure sensor 38 has exceeded an associated limit or operating conditions. of the current engine according to the present invention. An engine operation value, reference value or index value is determined from one or more engine operating parameters detected and / or calculated, including but not limited to engine speed (RPM) and torque of desired motor. As will be appreciated by one skilled in the art, the control logic in accordance with the present invention is preferably implemented by a programmed microprocessor which operates as described in detail below. However, various hardware and / or software alternatives may be used to implement the control logic without departing from the spirit or scope of the present invention. A data, diagnostic and programming interface 70 can be selectively connected to the controller 46 via a connector 72 to exchange different information between the controller 46 and the operator and / or service personnel. The interface 70 can be used to change values within the computer readable storage medium 52, such as configuration settings, calibration variables, look-up table values, control logic, pressure thresholds for detecting malfunctions of the motor and Similar. In operation, the open crankcase ventilation systems, as illustrated in Figure 1, have a crankcase pressure that varies as a function of engine power. During normal operation, the pressure inside the crankcase 36 will be much less than the pressure inside the combustion chamber 32. Several failures or malfunctions related to the cylinder / piston result in increased pressure within the crankcase 36. While certain Mechanical failures will result in an almost total loss of pressure within the combustion chamber 32 and an associated increase in crankcase pressure, most failures or malfunctions occur more gradually. As such, the present invention provides a system and method for discriminating between increases in crankcase pressure due to normal operating variations and those indicative of an imminent or gradual failure condition utilizing the crankcase pressure limit which varies as a function of the current engine operating conditions and can be adjusted or selected to accommodate various applications. In a preferred embodiment of the present invention, a malfunction or failure in the crankcase pressure is indicated when the measured crankcase pressure exceeds a corresponding limit value based on the current engine operating conditions. Preferably, the limit value is stored in a computer readable storage medium within an indexed search table by at least one measured and / or calculated motor operating parameter, such as the motor speed, the motor load ( indicated by the requested torque, for example), the power of the motor or the like. The sensitivity to the determination of a fault condition can be calibrated or adjusted by a corresponding calibration variable or variables so that sensitivity increases at higher speeds, or engine loads or approximately equal across all speeds and loads. Accordingly, the increased sensitivity of the present invention provides a system and method for detecting malfunctions on a scale of engine loads and engine speeds. In addition, the present invention provides timely detection and warning of malfunction before a catastrophic engine failure occurs to facilitate resolving action by the vehicle operator and / or engine controller. Referring now to Figure 2, there is shown a graph illustrating the calibration and operation of a motor malfunction detection system or method based on the crankcase pressure according to the present invention. The graph in Figure 2 represents the actual engine operation data for a six-cylinder diesel engine under normal operating conditions. The data 100 represented generally by lines 102, 104, and 106, represent CCP (kiloPascals) as a function of a motor operating parameter calculated based on the motor speed and the torque requested under "normal" operating conditions. "that is, without a crankcase pressure failure. The data 100 can be used to determine the corresponding crankcase pressure limit values 108 represented generally by line 110. The appropriate crankcase pressure limit value (CCPL) is used to determine when there is a crankcase pressure failure for the conditions of current motor operation as reflected by the selected motor operation parameter (EOP). The pressure limit of the crankcase 110 can be set theoretically or empirically using field tests, engine dynamometer tests, warranty data and the like. Likewise, the selection of an appropriate EOP indicative of a particular failure or faults can be selected based on a similar test and may vary based on the particular application and the particular failure. The crankcase pressure limit values are preferably sufficiently calibrated over the maximum anticipated crankcase pressure values that will be observed under normal operating conditions taking into account the variation from one engine to another. This will increase the constancy in a failure determination while reducing the likelihood of a false detection. Once the appropriate pressure limit or limits are established, one or more limit values 108 are stored in the computer readable storage medium 52, preferably in the form of a look-up table. As will be appreciated by one of ordinary skill in the art, several intermediate values can be determined by interpolation, extrapolation, or by calculating the usage parameters, values, or constants stored in the computer readable storage medium 52. In one embodiment of the present invention, a sensitivity or selection constant Kj is used to adjust the sensitivity of a fault determination. The graph in figure 2 represents a parameter of motor operation based on the motor speed and the required torque without a sensitivity adjustment, or equivalently with a K ^ of zero. As such, fault detection is more sensitive in pressure variations that occur at higher engine speeds. Curve 102 represents a line or curve of the constant motor speed (1350 RPM) as the required torque is varied from 0% (which corresponds inactive) to 100% (which corresponds to an acceleration of 100%). Likewise, the curves 104 and 106 represent the crankcase pressure measured as a function of a selected motor function parameter or reference value that is a function of a constant motor speed (1650 RPM and 1950 RMP, respectively) as the torque varies from 0% to 100%. In the mode of Figure 2, the motor operation parameter is represented by: EOP = (Nß * TQß + K1 * Nßi!) / (? * K2 + 1) Where Ne. represents the engine speed in revolutions per minute (RPM), (TQ) is the requested engine torque as indicated by the accelerator pedal position sensor, Ki is the sensitivity constant and K2 is a scale factor or normalization to scale EOP for several engines. In this example, Kj is zero and K2 represents the RPM limit of 2400. As such, the sensitivity of the crankcase pressure failure detection, that is, the change in CCP required to activate a fault condition, is adjusted to be more sensitive to faults that occur at higher engine speeds. This can be observed by the relatively smaller difference between the values of the curve 106 1950 RPM and the corresponding limit values compared to the values of curve 104 to 1650 RPM or curve 102 to 1350 RPM. According to the present invention, the detection sensitivity can be adjusted based on the particular configuration of the motor and / or the application to improve the capacity and reliability of the fault detection. Figure 3 illustrates the pressure data of the crankcase 120 as a function of an engine operating parameter (which is a function of the engine speed and the required torque) with a sensitivity factor or adjustment Kj selected to provide increased sensitivity for higher loads or torques required. In a preferred embodiment, K- \ is a one-byte calibration constant with a value between 0 (Hex) and FF (Hex) or equivalently 0 and 255 corresponding to scaled values ranging from 0 to 0.001275 represented by 5 * 10"6 per bit Figure 3 represents a value for K ^ of FF (Hex) and 2400 for K2 where the EOP is calculated as described above for Figure 2. The constant motor speed curves 122, 124 and 126 in addition to the crankcase boundary curve 128 (with representative values 130) are shown for comparison to figure 2. Constant motor (accelerator) load curves 132, 134 pass through corresponding points of engine speed curves constant 122, 124 and 126. Thus, the curve 132 represents the "normal" crankcase pressure values observed as a function of an engine operating parameter for a constant requested torque or accelerator pedal position as the engine speed from the inactive position up to 1950 RPM, while the curve 134 represents pressure values for a relatively constant lower accelerator pedal position as the engine speed varies from the inactive position to 1950 RPM. As such, a crankcase pressure failure condition, which is indicated when it is observed that the crankcase pressure exceeds the corresponding limit value for the current value of the selected engine operating value, is more sensitive to higher engine loads with relation to the sensitivity illustrated in Figure 2. Referring now to Figure 4, a crankcase pressure graph is shown as a function of a selected engine operating parameter with a sensitivity factor calibrated to provide approximately equal sensitivity to through all engine speeds and loads. The pressure limit curve of the crankcase 140 is shown in addition to the constant engine speed curves 142, 144 and 146 which correspond to the engine speeds of 1350, 1650 and 1950 RPM respectively, wide open throttle curve 148. As shown in FIG. It illustrates in curves 142, 144, 146 and 148 that they have corresponding values that are approximately equal across the operating range of the motor so that the difference between a value on any of those curves and the corresponding limit value is approximately the same. As such, the system will exhibit a substantially equal sensitivity for crankcase pressure failure across all engine speeds and loads. The illustrated data were generated with an EOP calculated as described above with reference to Figures 2 and 3 having a value for Ki of 30 (hex) or equivalently 48., and having a K2 value of 2400. As illustrated and described with reference to Figures 1 to 4, the present invention provides an adjustable motor operating parameter that can be referred to as an index value or reference value for access or select a pressure limit value of the corresponding crankcase, preferably stored in a search table. This provides adjustable sensitivity and flexibility in calibrating the crankcase pressure limit while minimizing the memory required to store the search table. Instead of adjusting the indexing variable (EOP), a two-dimensional or three-dimensional search table could alternatively be used, although clearly not as efficient in terms of memory utilization. In addition, a multidimensional search table requires significant development time to calibrate and validate compared to the preferred method of the present invention that utilizes a one-dimensional array or arrangement for storing the crankcase pressure limit values. Referring now to Figure 5, there is shown a flow chart showing the operation of a system and method for detecting engine malfunctions based on the crankcase pressure in accordance with the present invention. As will be appreciated by those with ordinary skill in the art, the flow diagram represents the control logic that can be implemented in hardware, software or a combination of hardware and software. The different functions are preferably performed by a programmed microprocessor, such as the DDEC controller, or which may include one or more functions implemented by dedicated integrated electronic, electrical circuits. As will also be appreciated, the control logic can be implemented using any one of a number of known programming and processing techniques and is not limited to the order or sequence illustrated here solely for convenience. For example, interrupt or event drive processing is typically employed in real-time control applications, such as control of an engine or vehicle transmission. Similarly, parallel processing, multi-tasking or multicarrier systems and methods can be used to achieve the objects, features and advantages of the present invention. The present invention is independent of the particular programming language, the operating system, processor, or circuits used to implement the illustrated control logic. The crankcase pressure (CCP) is measured as represented by the block 150. The current engine operating conditions are determined as represented by block 152. This may include the determination of the current engine speed (instantaneous or average) as represented by block 154 and / or the current requested motor torque as represented by block 156. A current index value is determined based on current motor conditions as represented by block 158. The value Index can be calculated using detected and / or calculated values that represent the current engine operating conditions. A limit value of the crankcase pressure is then determined based on the index value as represented by block 160. In other words, the index value defines the domain of the crankcase pressure limit function and the range is determined, preferably by means of a search table and the appropriate interpolation and / or extrapolation, as represented by block 160. Of course, the limit value could be calculated based on constants and appropriate operational variables, depending on the requirements of the particular application. The pressure value of the current crankcase is compared with the corresponding limit value as represented by block 162. The motor is then controlled based on the comparison result as represented by block 164. If the current value of the CCP is lower that or equal to the corresponding limit value, normal continuous operation as represented by block 166. If the current value for CCP exceeds the corresponding limit value as determined in block 164, then motor control can include the reduction of available motor torque as shown in FIG. represented by block 168, turning off the motor as represented by block 170, alerting the operator as represented by block 172 and / or recording a condition or fault code in the motor controller as represented by block 174. This code can then be used by the service personnel or operators of the automobile fleet in the diagnosis and correction of the fault condition. As recognized by one of ordinary skill in the art, the control logic illustrated in Figure 5 is executed or operated in a generally repeated manner whenever the engine is being operated. In a programmed microprocessor implementation, the control logic executed to sample the sensor signals in the determination of the current motor operating conditions and the crankcase pressure can be executed in a subordinate or secondary control cycle that is repeated approximately every 100 msec, for example. As such, the present invention provides a system and method for detecting a cylinder / piston failure based on the detected crankcase pressure. The present invention provides a set sensitivity to facilitate the timely detection of various failure conditions while reducing the susceptibility to false indications. The system memory is efficiently used by adjusting the index variable based on the desired sensitivity, preferably using a second order function of the required torque and motor speed. The present invention provides sensing sensitivity that can be adjusted to detect fault conditions more rapidly at higher engine speeds, higher engine loads or substantially equal across all engine speeds and loads. While the embodiments of the invention have been illustrated and described, these embodiments are not intended to illustrate and describe all possible forms of the invention. Instead, the wording used in the specification is a wording of description rather than limitation and several changes can be made without departing from the spirit and scope of the invention.

Claims (19)

1. A method to detect a malfunction of the engine in an internal combustion engine, the method comprising: detecting the crankcase pressure; determine the current engine conditions; determine an index value that has an adjustable sensitivity based on the current motor operating conditions; determine a crankcase pressure limit using the index value; compare the crankcase pressure with the crankcase pressure limit; and provide an indication of engine malfunction when the crankcase pressure exceeds the limit.

The method according to claim 1, characterized in that the determination of the current engine operating conditions comprises determining a current value for the engine speed.

3. The method according to claim 1, characterized in that the determination of the current engine operating conditions comprises determining a current value for the torque of the engine.

The method according to claim 3, characterized in that the determination of the current value for the motor torque comprises determining a current value for the requested motor torque.

5. The method according to claim 1, characterized in that the determination of an index value comprises determining an index value with an increased sensitivity to the motor speed.

The method according to claim 1, characterized in that the determination of an index value comprises determining an index value with a higher sensitivity for the motor torque.

The method according to claim 1, characterized in that the determination of an index value comprises determining an index value as a function of the requested motor speed and motor torque.

8. The method according to claim 1, characterized in that the determination of an index value comprises determining an index value according to: index = (TQe * Ne + K1 * Ne2) / (K1 * K2 + 1) where TQ represents a torque of motor, Ne represents the rotational speed of the motor, ^ represents an adjustable sensitivity constant and K2 represents a scaling constant.

9. A system for detecting a malfunction of the engine in an internal combustion engine, the system comprising: a first sensor for providing a continuously variable signal indicative of a crankcase pressure; a second sensor to determine the current engine operating conditions; a microprocessor in communication with the first and second sensors to determine a current crankcase pressure limit based on an index value having an adjustable sensitivity for the operating conditions of the engine, compared to the limit for a current crankcase pressure as it is indicated by the first sensor, and control the motor based on the result of the comparison stage.

The system according to claim 9, characterized in that the microprocessor controls the engine by reducing the available engine torque when the current crankcase pressure exceeds the limit.

The system according to claim 9, characterized in that the microprocessor controls the motor by stopping the motor when the current crankcase pressure exceeds the limit.

The system according to claim 9, further comprising: a computer readable storage medium in communication with the microprocessor and having the data stored thereon representing crankcase pressure limits accessed using the index value.

The system according to claim 9, further comprising: a computer readable storage medium having data representing the crankcase pressure limits accessed using the index value that varies in response to engine speed and torque of engine torque required.

14. A computer-readable storage medium having information stored thereon representing instructions executable by an engine controller in communication with a pressure transducer to detect the crankcase pressure and a sensor for detecting engine operating conditions for determine a malfunction of the engine based on the pressure of the crankcase, the computer readable storage medium comprising: instructions for detecting crankcase pressure; instructions to determine the current engine operating conditions; instructions for determining an index value having an adjustable sensitivity based on current engine operating conditions; instructions for determining a crankcase pressure limit using the index value; instructions for comparing the crankcase pressure with the crankcase pressure limit; and instructions to provide an indication of malfunction of an engine when the crankcase pressure exceeds the crankcase pressure limit.

15. The computer readable storage medium according to claim 14, characterized in that the instructions for determining the current engine operating conditions include instructions for determining the speed of the engine.

16. The computer readable storage medium according to claim 14, characterized in that the instructions for determining the current motor operating conditions include instructions for determining the required motor torque.

17. The computer readable storage medium according to claim 14, characterized in that the instructions for comparing the crankcase pressure include instructions for accessing a stored pressure limit of the crankcase based on the index value.

18. The computer readable storage medium according to claim 14, characterized in that instructions for determining an index value include instructions for determining an index value that is a function of the motor torque fraction and motor speed, including a second order term to adjust the sensitivity for the crankcase pressure variation in the crankcase pressure failure determination.

19. The computer readable storage medium according to claim 14, characterized in that the instructions for providing an indication of malfunction of the motor include instructions for reducing an available motor torque.