[001] The present subject matter described herein, relates to a system and a method for diagnosis of fault in brake vacuum pressure switch detector in brake system in vehicle, and in particularly, to a system and a method for diagnosis of a leakage fault in brake vacuum pressure switch of a vehicle having auto start and stop functionality. More particularly, the present subject matter relates to a system and a method for diagnosis of fault in brake vacuum pressure switch of brake system in a vehicle having auto start and stop functionality.
BACKGROUND AND PRIOR ART:
[002] In diesel engines, there is no throttle unit or it can be said that there is a wide open throttle (WOT). In gasoline engines, there is no Vacuum pump, vacuum is maintained by throttle either mechanical or electronic throttle control body. The engine will auto start when vacuum pressure in the booster is less than a particular threshold and Brake vacuum pressure switch is closed. Unlike diesel engines, in modern gasoline engines the accelerator pedal has accelerator pedal position sensor which senses the pedal position and sends signal to Engine Control Unit (ECU) for actuating the butterfly valve through solenoid operated throttle control actuator (operated by electronic throttle control unit). As the piston in the cylinder moves towards Bottom Dead Center (BDC) during the suction stroke negative pressure or vacuum is created in the intake manifold. Accordingly, air from the atmosphere enters the intake manifold due to pressure differential which is sensed by a mass air flow sensor which again sends signal to the ECU for proper fuel injection in the intake manifold where it mixes with the passing air forming fresh charge which then enters the combustion chamber. The vacuum brake booster is tapped with the intake manifold for Vacuum creation in its chambers.

[003] But diesel engines undergo fuel throttle and not air throttle. In other words, it does not have an air throttle control unit. At the end of the compression stroke fuel is injected in the form of fine mists through the orifice of the injectors which then vaporizes due to the high pressure and temperature prevailing in the cylinder and combustion takes place as the pressure and temperature in the engine cylinder is higher than the operating point of the fuel. The brake booster cannot be tapped to the intake manifold as in diesel engine due to the WOT intake air pressure is same all the time. The turbo charger runs the compressor which sends more air into the combustion chamber. After cranking the engine runs say at 700 rpm. During this time turbo doesn't operate it only starts after a definite speed say 1500 rpm. Some of the exhaust gas is bypassed through the waste gate of the turbine as per the demand and likewise the speed of the turbine and compressor is controlled.
[004] US published patent application US20090071147A1 titled "Brake Booster Leak Detection System" discloses a control system for evaluating a brake booster system includes an engine evaluation module that detects an engine off condition. A pressure evaluation module, during the engine off condition, monitors hydraulic brake line pressure, detects a change in brake booster pressure, and determines a brake booster vacuum decay rate based on the change in brake booster pressure. A fault reporting module detects a brake booster system fault based on the brake line pressure and the brake booster vacuum decay rate. The problem associated with the US application is that it detects the leak in the brake booster system which is implemented in the gasoline system taking vacuum pressure from the air intake manifold.
[005] To provide vacuum pressure in the brake booster system, in diesel vehicle or gasoline vehicle a Vacuum pump is coupled with the engine camshaft which maintains the vacuum in the brake booster. Accordingly, if the engine is not working then pump will not work as it is mechanically coupled with the camshaft. Thus, vacuum cannot be maintained in the booster for brake assist.

[006] In the brake booster whether there is vacuum or not is estimated by a brake pressure detector (switch) as per its open or closed condition. A brake pressure detector is a very critical component in a vehicle, based on which the safety and performance of the vehicle depends. The auto start stop functionality of a vehicle is influenced by the brake pressure switch. If there is any malfunction in the brake pressure detector, it will harm auto start stop functionality of engine. Therefore, a diagnosis of the brake vacuum pressure switch failure (OC) is necessary.
[007] Therefore, it is beneficial to have a system which detect/diagnose malfunction or failure of the brake vacuum pressure detector (switch) in the brake system efficiently.
OBJECTS OF THE INVENTION:
[008] The principal object of the present invention is to provide a system for diagnosis of failure of brake vacuum pressure detector (switch) in brake system of vehicle.
[009] Another object of the present invention is to provide a method for diagnosis of failure of brake vacuum pressure switch in brake system of vehicle.
[0010] Another object of the present subject matter is to provide a method and a system in Engine Control Unit (ECU) which uses hardware elements of the ECU to diagnosis the failure of the brake vacuum pressure switch.
[0011] Yet another object of the present invention is to provide a simple and inexpensive system for diagnosis real time failure of the brake vacuum pressure switch in the brake system.
SUMMARY OF THE INVENTION:
[0012] The subject matter disclosed herein relates to a system and a method detecting or diagnosis of malfunction in brake vacuum pressure switch of brake booster in vehicle. The brake vacuum pressure switch of brake booster has two states one is open and other is closed. The possibility of switch for normally close or normally open depends on the manufacturer. For normally open type switch open state of switch means that there is Vacuum in the booster and closed state

means that there is no vacuum in the booster. Switch is normally open, closes when there is loss of vacuum. For normally closed type switch, open state means there is no vacuum and switch close means where there is vacuum. Switch is normally closed, opens when there is loss of vacuum. In the description, let us consider normally open type switch. If the brake vacuum pressure switch is in close state, it means that there is no vacuum in the brake booster. If the brake pressure switch is in open state it means there is vacuum in the brake booster. In the vehicles, brake vacuum pump is coupled with camshaft of the engine to generate vacuum pressure in the brake booster. The vacuum leakage time period, which is the vacuum inside the brake booster depletes along with time through leakages considering no mechanical seals and joints are perfectly air tight. When the vehicle engine is in Off condition, i.e., ignition Off the soaking time period starts and if the soaking time period is more than the vacuum leakage time the brake pressure switch should be in closed state indicating there is no vacuum in brake booster. If the brake switch is in open state, it indicates that there is an error in the brake pressure switch. The ECM will always get an indication that there is vacuum intact or within permissible limits in the booster and autostart will not take place. The present system and method diagnosis such problem and indicate the same to the vehicle operator for correction.
[0013] In an embodiment of the present subject matter, a brake vacuum pressure switch diagnostic system (BVPSD) is implemented in Engine control unit (ECU) to diagnosis or detect malfunction in the brake vacuum pressure switch. The present system uses microcontroller and memory of the ECU to detect the malfunction. The BVPSD system comprises a microcontroller which is communicatively coupled with a memory for storing instruction(s) and data. The BVPSD system has a counter increment block to increase a counter CI by one when vehicle engine starts after vacuum leakage time period days (x) and a brake pressure switch open circuit fault detection module which detects condition of the brake pressure switch in brake booster and determines whether the brake pressure switch is in open state or in close state. When the brake pressure switch is in open state, the brake pressure switch open circuit fault detection module increases a

counter C2 by one and determines whether the counter C2 is greater than half of the counter C1. Further, the system has a fault reporting module which detects malfunction in the brake vacuum pressure switch based on combination of output of the brake pressure switch open circuit fault detection module and the counter 5 increment block.
[0014] In another embodiment of the present subject matter, a method is implemented in the ECU for execution to diagnosis or detect malfunction in the brake vacuum pressure switch. In the present method, counter increment block increases a counter C1 by one when vehicle engine starts after vacuum leakage
10 time period days (x) and a microcontroller determines condition of the brake pressure switch. Further, an open circuit switch counter increment block increases an error counter C2 by one when brake pressure switch is in open state, as in switch is conveying inaccurate message to the ECU. The method compares the counter (C2) with half of threshold value of the counter (C1) and generates a
15 malfunction light (flag) when the counter C2 is greater than or equal to the half of threshold value of the counter C1.
[0015] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative 20 only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally 25 effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with
6

embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0017] Fig. 1 illustrates schematic diagram brake pressure switch diagnosis (BPSD) system of a vehicle with Engine Control Unit, in accordance with an 5 embodiment of the present subject matter;
[0018] Fig. 2 illustrates the ECU working along with engine and other hardware components to detect or diagnosis failure of the brake pressure switch, in accordance with an embodiment of the present subject matter; and
[0019] Fig. 3a-3d illustrate a method for diagnosing failure of brake vacuum 10 pressure switch in brake system, in accordance with an embodiment of the present subject matter.
[0020] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and 15 methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0021] The subject matter disclosed herein relates to a system and a method detecting or diagnosis of malfunction in brake pressure switch of brake booster in
20 vehicle. The brake pressure switch of brake booster has two states one is open and other is close. There are two possibilities of switch for normally close or normally open. In the description, let us consider normally close type switch. If the brake vacuum pressure switch is in open state, it means that there is vacuum in the brake booster. If the brake pressure switch is in closed state it means there is no vacuum
25 in the brake booster. In the vehicles, brake vacuum pump is coupled with camshaft of the engine to generate vacuum pressure in the brake booster. The vacuum leakage time period, which is the vacuum inside the brake booster depletes along with time through leakages considering no mechanical seals and joints are perfectly air tight. When the vehicle engine is in Off condition, i.e.,
7

ignition Off the soaking time period starts and if the soaking time period is more than the vacuum leakage time the brake pressure switch should be in closed state indicating there is no vacuum in brake booster. If the brake switch is in open state, it indicates that there is an error in the brake pressure switch. Due to error in the 5 brake pressure switch, the vehicle engine will not undergo auto start as the ECM will get an indication that vacuum in the booster is intact or within permissible limits in the booster and auto start will not take place. The present system and method diagnosis such problem and indicate the same to the vehicle operator for correction.
10 [0022] In an embodiment of the present subject matter, a brake vacuum pressure switch diagnostic system (BVPSD) is implemented in Engine control unit (ECU) to diagnosis or detect malfunction in the brake vacuum pressure switch. The present system uses microcontroller and memory of the ECU to detect the malfunction. The BVPSD system comprises a microcontroller which is
15 communicatively coupled with a memory for storing instruction(s) and data. The BVPSD system has a counter increment block to increase a counter C1 by one when vehicle engine starts after vacuum leakage time period days (x) and a brake pressure switch open circuit fault detection module which detects condition of the brake pressure switch in brake booster and determines whether the brake pressure
20 switch is in open state or in close state. When the brake pressure switch is in open state, the brake pressure switch open circuit fault detection module increases a counter C2 by one and determines whether the counter C2 is greater than half of the counter C1. Further, the system has a fault reporting module which detects malfunction in the brake vacuum pressure switch based on combination of output
25 of the brake pressure switch open circuit fault detection module and the counter increment block.
[0023] In another embodiment of the present subject matter, a method is
implemented in the ECU for execution to diagnosis or detect malfunction in the
brake vacuum pressure switch. In the present method, counter increment block
30 increases a counter C1 by one when vehicle engine starts after vacuum leakage
8

time period days (x) and a microcontroller determines condition of the brake pressure switch. Further, an open circuit switch counter increment block increases an error counter C2 by one when brake pressure switch is in close state, as in switch is conveying inaccurate message to the ECU. The method compares the 5 counter (C2) with half of threshold value of the counter (C1) and generates a malfunction light (flag) when the counter C2 is greater than the half of threshold value of the counter C1 or the counter C2 is equal to the half of the counter (C1).
[0024] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled
10 in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject
15 matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and
20 conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
25 [0025] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the
30 principles of the present subject matter and are included within its scope.
9

[0026] Fig. 1 illustrates schematic block diagram of the present vacuum brake pressure switch diagnosis (BVPSD) system of a vehicle within Engine Control Unit along with hardware embodiments, in accordance with an embodiment of the present subject matter. The BVPSD system 104 is implemented inside an Engine
5 Control Unit (ECU) 100 of the vehicle. The ECU 100 has a processor 103, hardware interface 102, and a memory 101 for storing logics and doing calculations to determine the objective of the present subject matter. The BVPSD System 104 is configured within Engine Control Unit (ECU) 100 of the vehicle. The processor 103 which is communicatively coupled with hardware interface
10 102, a memory 101, and a BVPSD system 104 for diagnosis of failure of brake vacuum pressure switch (detector). The BVPSD system 104 is coupled with the processor 103 for receiving a plurality of inputs from coolant temperature sensor 105, atmospheric pressure sensor 108, and brake system 109. The BVPSD system 104 is coupled with the coolant temperature sensor 105 and the atmospheric
15 pressure sensor 108 to determine vacuum leakage time period for the system. The BVPSD system 104 is coupled with the coolant temperature sensor 105, the atmospheric pressure sensor 108, and brake system 109 via the hardware interface 102.
[0027] The processor(s) 103, may be implemented as one or more
20 microprocessors, microcomputers, microcontrollers, digital signal processors,
central processing units, logic circuitries, and/or any devices that manipulate
signals based on operational instructions. Among other capabilities, the
processor(s) 103 is configured to fetch and execute computer-readable instructions
stored in the memory 101. The functions of the various elements shown in the
25 figure, including any functional blocks labeled as “processor(s)”, may be provided
through the use of dedicated hardware as well as hardware capable of executing
computer readable instructions or logics in association with appropriate module.
When provided by a processor, the functions may be provided by a single
dedicated processor, by a single shared processor, or by a plurality of individual
30 processors, some of which may be shared. Moreover, explicit use of the term
“processor” should not be construed to refer exclusively to hardware capable of
10

executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), non-volatile storage. Other 5 hardware, conventional and/or custom, may also be included.
[0028] The hardware interface 102 may include a variety of software and hardware interfaces, for example, interfaces for peripheral device(s), such as sensors, actuators, and an external memory. The hardware interface 102 is suitable for interfacing with the sensor as referred in the figure 1 and 2. The memory 101
10 can include any computer-readable medium known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), and/or non-volatile memory, such as read only memory (ROM), erasable programmable ROM, flash memories, hard disks, optical disks, and magnetic tapes. A person skilled in the art is well aware
15 about the construction of the ECU 100. The processor 103 is operatively coupled with the memory 101 and the hardware interface 102 to execute the instructions for running the ECU 100. These instruction or logics may be encoded in the programs that are stored in the memory 101. Further, all the output of the system and calculation of the ECU also stores in the memory 101 for future
20 determinations.
[0029] The ECU 100 is coupled with the battery 107 to receive power for running a clock inside the ECU 100. Further, the BVPSD system 104 is coupled with dashboard display unit 106 to display output of the diagnosis of the brake system.
[0030] Figure 2 illustrates block diagram of vehicle with brake system and ECU 25 having BVPSD system according to various aspects of the present subject matter. The vehicle 200 can be diesel vehicle or gasoline vehicle. The vehicle may have auto start stop functionality which depends on the working condition of the brake booster of the brake system. The vehicle 200 as shown in FIG. 2 includes an engine 201 that drives a transmission. The engine 201 may have a plurality of 30 cylinders N. Although FIG. 2 depicts four cylinders (N=4), it can be appreciated
11

that the engine 201 may include additional or fewer cylinders. For example, the engine 201 may have 4 6, 8, 10, and 12 cylinders. Further, the engine 201 is coupled with the air intake manifold 202 to receive air for fuel air mixture for combustion in the engine cylinders. Further, a brake vacuum pump 204 is coupled
5 with engine camshaft. The brake vacuum pump 204 maintain vacuum in brake booster. Based on the present configuration, if engine is not working then pump will not work as it is mechanically coupled with the camshaft. Thus, vacuum cannot be maintained in the booster for the brake assist. The brake vacuum pump 204 is coupled with the brake booster 205 to assist braking system. Further, a
10 brake vacuum pressure switch 206 is provided in the brake booster 205 which release the vacuum pressure during usage of the brake system, in particular to brake pedal.
[0031] In an embodiment of the present subject matter, Engine Control Unit (ECU) 300 is coupled with the brake vacuum pressure switch 206 via hardware
15 interface. The ECU 300 comprises a microcontroller 302 which is a processor and a brake vacuum pressure switch diagnostic (BVPSD) system 301. The ECU 300 further comprises a soaking module 303, counter initialization module 304, counter increment block 305, Open Circuit (OP) Switch (sw) counter increment block 306, brake pressure switch OC fault detection module 307, and a fault
20 reporting module 308 which are embodiment of the BVPSD system 301. The ECU 300 is coupled with coolant temperature sensor 208, atmospheric pressure sensor 209, and battery 210.
[0032] In another embodiment, the BVPSD system 301 comprises soaking module 303, counter initialization module 304, counter increment block 305, 25 Open Circuit (OP) Switch (sw) counter increment block 306, brake pressure switch OC fault detection module 307, and a fault reporting module 308. All these modules are coupled with the each other through the microcontroller 302 to diagnosis malfunction in the brake vacuum pressure switch 206.
[0033] In an embodiment, the microcontroller 302 detects open and close 30 condition of the brake pressure switch 206 and provide the detected information to
12

Atmospheric pressure
100Kpa 110 Kpa 90 Kpa
Coolant temperature HIGH TEMP 10 days 20 days 8 days

ROOM TEMP .v rite's

LOW TEMP
the BVPSD system 301. The soaking module 303 calculates the vacuum leakage time or idle time of the engine when the vehicle engine stops and the driver turns the key to ignition off condition the ECU 300 enters into a standby mode where a timer/counter ticks. The soaking module 303 receives inputs of the coolant 5 temperature sensor 208 and the atmospheric pressure sensor 209 calculates vacuum leakage time. For example, the soaking module 303 calculates vacuum leakage time as x days. The vacuum leakage time x is mapped to the BVPSD system 301 for initialization. Further variation of x with atmospheric pressure and temperature:
10 The vacuum leakage time can be calculated in hours or days.
[0034] It is expected that the vacuum in the brake booster 205 will be gradually lost as atmospheric air will be slowly entering the booster through some leakages considering no mechanical seals and joints are perfectly air tight. It is assumed that vehicle operator has not depressed or pressed the brake pedal in the soaking
15 period. After Y days of soaking which is greater than the determined vacuum leakage period x, if the brake pressure switch 206 is open state which actually is false condition, the ECU 300 gets a feedback signal that there is vacuum in the booster but actually there is no Vacuum or the Vacuum pressure is lesser than the permissible limit for the brake booster 205 to work on in actual scenario. This can
20 be a problem for auto start/stop functionality in the vehicle. Considering an auto start-stop vehicle, in general when the brake pressure is low (brake pressure switch is closed) during an auto-stop, the engine automatically restarts without driver intervention. The closed state of the brake switch in the booster indicating vacuum pressure low or no vacuum. However, if the Brake switch is open
25 permanently OC-open circuit then the ECU 300 will find that there is safe permissible vacuum in the booster and the engine will not auto-restart even when the brake pressure is low.
13

[0035] In case of false indication by the brake pressure switch, such as open state when there is no Vacuum pressure, it creates problem in auto start stop functionality of the vehicle.
[0036] The primary objective of the present system and method is to detect 5 malfunction in the brake pressure switch.
[0037] Once the soaking period/time is calculated, the BVPSD system 301 is activated to detect the malfunction in the brake pressure switch 206. The counter initialization module 304 initializes a counter C1 equal to zero in the BVPSD system 301. Whenever, vehicle operator makes ignition ON after the vacuum
10 leakage time period which is variable parameter, the ECU 300 activates the BVPSD system 301 for diagnosis of failure or malfunction in the brake vacuum pressure switch 206. The counter increment block 305 increases the counter C1 by one if condition is fulfilled. Further, the BVPSD system 301 has another error counter C2 for the open circuit switch situation. The OC SW counter increment
15 block 306 increases the error counter C2 by one based on the received inputs. If the brake pressure switch 206 is in close state which has to be in open state due to soaking time period, the OC SW counter increment block 306 increases the error counter C2 by one.
[0038] The brake pressure switch OC fault detection module 307 detects error in
20 the brake pressure switch when predefined conditions are met (disclose in figure
3). Upon detection of the malfunction in the brake pressure switch 206, the fault
reporting module 308 generate a flag which activates malfunction light in the
dashboard display unit 212. The dashboard display unit 212 is provided in the
instrument panel of the vehicle along with speedometer. Further, it can be
25 provided in a separate place on the dashboard. The dashboard display unit 212
displays the malfunction at every Ignition On condition. Once the brake pressure
switch is healed, the malfunction light dis-appear from the dashboard display unit
212 and initialize the counter C1 as zero for continues detection of malfunction of
the brake pressure switch 206. The counter C1 automatically reset when reaches
30 to the maximum value. Simultaneously, counter C2 gets reset when counter C1
14

gets rest. The maximum value of counter C1 is pre-defined value. Once the OBD is healed, the system will reset both counter C1 and C2.
[0039] Referring to fig. 3 which describes a method for diagnosis/detecting malfunction in brake pressure switch in brake booster, in accordance with an
5 embodiment of the present subject matter. The method discloses how the present BVPSD system 301 works to enable diagnosis of malfunction in brake vacuum pressure switch based on real time parameters of the brake pressure switch. As per the present method, the ECU (Engine Control Unit) 300 having the BVPSD system 301 calculates vacuum leakage time based on certain defined conditions to
10 activate diagnosis of malfunction.
[0040] Referring to step 401 of the figure 3a, when the vehicle is in Ignition Off condition, the BVPSD system 301 calculates the ignition off time with a timer. At step 403, the coolant temperature sensor 108 determines temperature of the coolant and sends the determined value to the BVPSD system 301. At the step 15 402, the atmospheric pressures sensor 209 determines atmospheric pressure and sends the determined value to the BVPSD system 301. At the step 404, the soaking module of the BVPSD system 301 calculates the vacuum leakage time period, i.e., x days and saves the calculated soaking time period into the memory of the ECU 300.
20 [0041] Referring to figure 3b, at step 501 the BVPSD system 301 wakes after every T interval of time and calculate total time after ignition off soaking time at step 502.
[0042] Referring to figure 3c, at step 601 and 602 respectively, the BVPSD system 301 wakes up and calculate time after ignition off soaking time period.
25 The BVPSD system 301 determines whether the vehicle engine starts after ‘y’ days which are more than the calculated vacuum leakage time period x days. When y days are more than or equal to the calculated vacuum leakage timer period x days, the BVPSD system 301 moves further to step 604 to check whether the counter C1 is more than the predefined value checkmax. If the value of the
30 counter C1 is more than the predefined value of C1 checkmax, the BVPSD system
15

301 moves to step 605 where the counter C1 and C2 are reset to zero. If the counter C1 is less than or equals to the threshold value checkmax, the BVPSD system 301 moves further step 606 where the counter C1 is increased by one. . If y days are less than the calculated vacuum leakage time period x days, the BPSD 5 system proceeds to step 407 where no action is taken by the ECU 300.
[0043] At step 607, the BVPSD system 301 checks whether the brake vacuum pressure switch is in open or close state. If the break vacuum pressure switch is in closed state which is true condition, the method proceeds to step 611 where the BVPSD system 301 do not take any action. If the brake vacuum pressure switch is 10 in open state which is false condition based on the vacuum leakage time period, the method proceeds to step 608.
[0044] At the step 608, the BVPSD system 301 specifically, the OC switch counter increment block 306 increases the error counter C2 by one and stores the updated error counter C2 in the memory of the ECU 300.
15 [0045] At step 609, the brake pressure switch OC fault detection module 307 compares the error counter C2 with the half of the counter C1. If the error counter C2 is less than half of the counter C1, the brake pressure switch OC fault detection module 307 detects no error in the brake vacuum pressure switch and proceed to step 611. If the error counter C2 is more than half of the counter C1,
20 the brake pressure switch OC fault detection module 307 detects an error in the brake vacuum pressure switch and proceed to step 610 where a flag is generated to indicating the error in the display unit 212 coupled with the BVPSD system 301.
[0046] Referring to figure 3d, the method 700 describes healing process of the 25 error. After detection of the error in the brake vacuum pressure switch, an error is displayed in the display unit every time when the ignition is ON, at step 701. At step 702, the BVPSD system 301 checks whether error has been healed or not. If not, the error display remains same in the display unit and prompt the same. If the error has been healed, the BVSPD system 301 reset the counter C1 to zero at step
16

704. At step 705, the BVPSD system 301 reinitialize the error counter C2 to zero and restart the diagnosis process at step 706.
[0047] In an embodiment, the present method for detecting malfunction in brake vacuum pressure switch 206 comprises
5 increasing 606, by counter increment block 305, a counter C1 by one
when vehicle engine starts after vacuum leakage time period days (x);
determining 607, by a microcontroller 302, condition of the break vacuum pressure switch 206;
increasing608, by open circuit switch counter increment block 306, a 10 error counter C2 by one when brake pressure switch 206 is in close state;
comparing609, by brake pressure switch open circuit fault detection module 307, the error counter (C2) with half of threshold value of the counter (C1);
generating 610, by a fault reporting module 308, a malfunction light 15 (flag) when the error counter C2 is greater than the half of threshold value of the counter C1;
illuminating, by the fault reporting module (308), the malfunction light on dashboard display unit 212.
20 [0048] In an embodiment, the method 700 re-initializing 704, by the brake pressure switch open circuit fault detection module 307, the counter (C1) to zero and the error counter C2 when the brake vacuum pressure switch is healed.
[0049] The present method and system is also applicable for switch which works in opposite concept of the close and open state.
25 [0050] The term “vehicle” as used throughout this detailed description and in the claims refers to any moving vehicle that is capable of carrying one or more human occupants and is powered by any form of energy. The term “vehicle” is a motor
17

vehicle which includes, but is not limited to: cars, trucks, vans, minivans, hatchback, sedan, MUVs, and SUVs.
[0051] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.

We claim:

A brake vacuum pressure switch diagnostic (BVPSD) system (301) implemented in Engine Control Unit (300) to diagnosis malfunction in brake pressure switch (206), the BPSD system (301) comprising: a microcontroller (103, 302) communicatively coupled with:
a counter increment block (305) to increase a counter (CI) by one when vehicle engine starts after vacuum leakage time period days (x);
a brake vacuum pressure switch open circuit fault detection module (307) detects condition of the brake pressure switch (206) in brake booster (205) and determines whether the brake pressure switch (206) is in open state or in close state,
when the brake pressure switch (206) is in error state, the brake pressure switch fault detection module (307) increases an error counter (C2) by one and determines whether the error counter (C2) is greater than half of the counter (CI);
a fault reporting module (308) detects malfunction in the brake pressure switch (206) based on combination of output of the brake pressure switch circuit fault detection module (307) and the counter increment block (305).
The BVPSD system (301) as claimed in claim 1, wherein the fault reporting module (308) illuminate malfunction light on dashboard display unit (212) to indicate malfunction in the brake pressure switch (206).
The BVPSD system (301) as claimed in claim 2, wherein the fault reporting module (308) continuously illuminate the malfunction light on the dashboard display unit (212) until healed.

The BVPSD system (301) as claimed in claim 1, wherein the counter increment block (305) increases the counter (CI) by one after every vacuum leakage time period (x) days.
The BVPSD system (301) as claimed in claim 1, wherein the brake pressure switch fault detection module (307) initialize the counter (CI) to zero upon detection that the counter (CI) is less than to the threshold value of the counter check max.
A method (600, 700) for detecting malfunction in brake pressure switch (206), the method (600) comprising:
increasing (606), by counter increment block (305), a counter (CI) by one when vehicle engine starts after vacuum leakage time period days (x);
determining (607), by a microcontroller (302), condition of the break pressure switch (206);
increasing (608), by open circuit switch counter increment block (306), an error counter (C2) by one when brake pressure switch (206) is in open state;
comparing (609), by brake pressure switch open circuit fault detection module (307), the error counter (C2) with half of threshold value of the counter (CI);
generating (610), by a fault reporting module (308), a malfunction light (flag) when the error counter (C2) is greater than the half of the counter (CI) or the error counter (C2) is equal to half of the counter (CI).
The method (600, 700) as claimed in claim 6, wherein the method (600, 700) further comprises illuminating (703), by the fault reporting module (308), the malfunction light on dashboard display unit (212).

The method (400) as claimed in claim 6, wherein the method (600, 700) further comprises:
re-initializing (605), by the brake pressure switch open circuit fault detection module (307), the counter (CI) to zero when the counter (CI) is less than the counter checkmax.
The method (600, 700) as claimed in claim 6, wherein the method (600, 700) further comprises:
re-initializing (704), by the fault reporting module (308), the counter (CI) when malfunction in the brake vacuum pressure switch (206) is resolved.
The method (600, 700) as claimed in claim 6, wherein the method (600, 700) is implemented in electronic control unit (300).
The method (600, 700) as claimed in claim 6, wherein the method (400) further comprises:
calculating (404), by soaking module (303), vacuum leakage time period (x days) based on inputs received from atmospheric pressure sensor (209) and coolant temperature sensor (208).