Methods and systems for loss of communication detection in a vehicle network

Methods and systems are provided for detecting loss of communication in a vehicle network. In one example, a method may include determining a diagnostic time threshold based on an estimated duration for failure of vehicle operation under current operating conditions due to a loss of communication with a control module in the vehicle network. Further, in response to a duration of loss of communication exceeding the time threshold, a loss of communication DTC may be activated.

FIELD

The present description relates generally to methods and systems for detecting loss of communication in a vehicle network.

Vehicle systems may be equipped with a plurality of vehicle control modules that receive information from vehicle electronic sensing devices and communicate regulatory information to actuators. Further, vehicle systems may be configured with vehicle data networks for data exchange and communication among the vehicle control modules, and between the vehicle control modules and associated sensors and actuators.

One example of vehicle data network is a controller area network (CAN), which is a shared serial bus system connecting the various vehicle control modules. When there is a loss of communication between the modules, information may be unavailable for arbitration and execution of vehicle actions. Therefore, vehicle systems may include an on-board diagnostic (OBD) system for monitoring vehicle operations, as well as for monitoring the vehicle network and diagnosing faults in network communication. Upon detecting loss of communication from a control module for a predetermined duration threshold (e.g., 5 seconds), the OBD system may activate a diagnostic trouble code (DTC) corresponding to the nature of fault detected.

However, the inventors herein have identified potential issues with such an approach. For example, by utilizing the predetermined duration threshold, loss of communication in the network may result in a failure in vehicle operation (due to loss of information for execution of vehicle operation) prior to the activation of a loss of communication DTC. As a result, the vehicle may enter a failure mode before the loss of communication DTC is set. Consequently, the loss of communication may not be detected leading to difficulty in diagnosing the actual cause of vehicle failure, and causing delays in problem solving. As an example, when there is a loss of communication from a fuel pump electronics module (PEM), the vehicle may stall due to lack of torque before the OBD system activates a loss of communication DTC for PEM (e.g., a U0109 code).

In one example, some of the above issues may be at least partly addressed by a method for a vehicle, comprising: determining a first time threshold for a setting a loss of communication diagnostic trouble code based on an estimated duration for loss of vehicle operation due to a loss of communication from a first module connected to a vehicle network connecting a plurality of control modules in the vehicle.

As an example, a plurality of control modules regulating one or more vehicle operations may be connected via one or more vehicular network bus for data exchange and communication. Communication from the control modules may be monitored and upon detecting a loss of communication from a control module, an estimated duration for failure of vehicle operation due to the loss of communication may be determined. Further, a time threshold for activating a loss of communication DTC may be determined based on the estimated duration for failure so as to activate the loss of communication DTC prior to occurrence of vehicle failure due to the loss of communication.

In this way, intelligent decisions for setting loss of communication DTCs may be executed by adjusting the time threshold for setting the loss of communication DTC based on the estimated duration for vehicle operation failure. As a result, loss of communication faults may be detected prior to the vehicle entering a failure mode, thereby improving loss of communication diagnosis and enabling faster problem solving.

DETAILED DESCRIPTION

The following description relates to systems and methods for loss of communication in a vehicle network such as the vehicle network shown inFIG. 1including an engine system and a fuel system ofFIG. 2. One or more controllers in the vehicle network may be configured to perform a control routine, such as routine ofFIG. 3to set a diagnostic time code in response to detecting loss of communication from one or more modules in the network according to the routines ofFIGS. 4A-4B. Further, a diagnostic time threshold for setting the diagnostic time code may be determined based on the routine ofFIG. 5. An example setting of the loss of communication diagnostic time code according to the present disclosure is shown atFIG. 6.

Turning toFIG. 1, an example embodiment of motor vehicle102equipped with a vehicle network system110connecting a plurality of control modules114is illustrated schematically. Motor vehicle102may be a road automobile, among other types of vehicles. Vehicle102includes drive wheels105, a windshield101, side view mirrors103, and an internal combustion engine10. Internal combustion engine10includes a combustion chamber (not shown) which may receive intake air via an intake passage (not shown) and may exhaust combustion gases via exhaust passage (not shown).

Motor vehicle102further includes vehicle network system110including plurality of control modules114communicating via a network bus130and regulating various vehicle operations. A bus communication may include a controller area network allowing flexible network configurations based on different types of microprocessors and microcontroller. The plurality of control modules114may include but are not limited to active grille shutter module (AGS)132, restraints control module (RCM)134, engine control module (ECM)136, anti-lock brake system module (ABS)138, engine coolant pump control module (EWPM)139, heating-ventilation-air conditioning control module (FCIM)140, steering column control module (SWCM)142, instrument panel cluster control module (IPCM)144, cruise control module (ICCM)146, body control module (BCM)148, transmission control module (TCM)150, battery energy control module (BECM)152, hybrid powertrain control module (HPCM)154, and fuel pump electronics control module (PEM)156. The network bus may operate utilizing one or more communication protocols such as a controller area network (CAN) protocol, or a fiber optic media oriented systems transport ring (MOST) protocol. The modules may communicate in a peer-to-peer configuration. Alternatively, a master-slave configuration may be utilized.

In the given example, one network communication bus130is shown. However, it must be appreciated that the network communication bus may further communicate with one or more additional communication bus each including one or more additional control modules.

Each of the control modules114may be communicatively coupled to various components of vehicle100including engine10to carry out the control routines and actions described herein. Further, each of the control modules114connected to network bus130may include its own electronic digital controller112. Controller112may be a microcomputer, including a microprocessor unit, input/output ports, an electronic storage medium for executable programs and calibration values, random access memory, keep alive memory, and a data bus.

As depicted, each controller112included in each control module may receive input from a plurality of sensors116, which may include one or more of user inputs and/or sensors (such as barometric pressure, transmission gear position, transmission clutch position, gas pedal input, brake input, transmission selector position, vehicle speed, engine speed, mass airflow through the engine, ambient temperature, intake air temperature, etc.), climate control system sensors (such as coolant temperature, adsorbent temperature, fan speed, passenger compartment temperature, desired passenger compartment temperature, ambient humidity, etc.), and others.

Further, controller112may communicate with various actuators124, which may include one or more of engine actuators (such as fuel injectors, an electronically controlled intake air throttle plate, spark plugs, transmission clutches, etc.), climate control system actuators (such as air handling vents and/or diverter valves, valves controlling the flow of coolant, blower actuators, fan actuators, etc.), and others. In addition, controller112may receive data from a global positioning system and/or an in-vehicle communications and entertainment system of vehicle100.

Further, the vehicle network110may be communicatively coupled to an off-board network (not shown) such as a cloud computing system via wireless communication, which may be Wi-Fi, Bluetooth, a type of cellular service, or a wireless data transfer protocol.

Further, the vehicle network110may include a diagnostic module for monitoring communication from each of the control modules114in the network, detecting loss of communication from the control modules, and setting DTCs (e.g. loss of communication DTCs). In some examples, additionally or alternatively, each of the control modules may include a secondary control module for monitoring communication, detecting loss of communication from the control modules, and setting DTCs. Example control routines for monitoring communication from the modules, detecting loss of communication from the modules, and setting loss of communication DTCs may be stored in a diagnostic controller of the diagnostic module and/or in a secondary controller the secondary module and will be further elaborated with respect toFIGS. 3-5.

As such, during certain engine operating conditions, there may be loss of communication from one or more control modules in the network. Consequently, information may be unavailable for arbitration and execution of associated vehicle actions which may lead to failure in vehicle operation. Further, the failure may occur prior to activation of a loss of communication DTC. Therefore, in order to activate the loss of communication DTC prior to failure of vehicle operation, a diagnostic time threshold (that is, minimum duration of loss of communication after which loss of communication DTC may be set) for setting loss of communication DTC may be based on an estimated duration for failure due to the loss of communication. For example, the diagnostic time threshold for setting loss of communication DTC may be less than the estimated duration for failure. Details of determining the diagnostic time threshold and setting the loss of communication DTC will be further elaborated with respect toFIGS. 3-6.

In one example, the system ofFIG. 1provides for a vehicle system, comprising: a plurality of electronic control modules regulating a plurality of vehicle operations, each of the plurality of control modules communicating with a controller area network bus of a vehicle control system; a monitor line communicating diagnostic data between a first control module and an electronic control module of the plurality of control modules; a controller with computer readable instructions stored in non-transitory memory for: detecting a loss of communication from the first module based on detecting an error state of the monitor line; in response to detecting the loss of communication, adjusting a first time constant based on an estimated time for vehicle failure to occur due to a loss of communication from a first module; and wherein the loss of communication is determined based on an error state of the monitor line.

The system further includes wherein adjusting the first time constant includes reducing the time constant to less than the estimated time; and wherein the controller includes further instructions for setting a loss of communication diagnostic time code in response to a counter exceeding the adjusted time constant, and shifting vehicle operation to a failure mode in response to setting the loss of communication diagnostic code; and wherein the counter is started in response to detecting the loss of communication from the first module via the monitor line.

FIG. 2shows a schematic depiction of a hybrid vehicle system6that can derive propulsion power from engine system8and/or an on-board energy storage device, such as a battery system (not shown). An energy conversion device, such as a generator (not shown), may be operated to absorb energy from vehicle motion and/or engine operation, and then convert the absorbed energy to an energy form suitable for storage by the energy storage device.

Engine system8may include an engine10having a plurality of cylinders30. Engine10includes an engine intake23and an engine exhaust25. Engine intake23includes an air intake throttle62fluidly coupled to the engine intake manifold44via an intake passage42. Air may enter intake passage42via air filter52. Engine exhaust25includes an exhaust manifold48leading to an exhaust passage35that routes exhaust gas to the atmosphere. Engine exhaust25may include one or more emission control devices70mounted in a close-coupled position. The one or more emission control devices may include a three-way catalyst, lean NOx trap, diesel particulate filter, oxidation catalyst, etc. It will be appreciated that other components may be included in the engine such as a variety of valves and sensors, as further elaborated in herein. In some embodiments, wherein engine system8is a boosted engine system, the engine system may further include a boosting device, such as a turbocharger (not shown).

Engine system8is coupled to a fuel system18. Fuel system18includes a fuel tank20coupled to a fuel pump21and a fuel vapor canister22. During a fuel tank refueling event, fuel may be pumped into the vehicle from an external source through refueling door108. Fuel tank20may hold a plurality of fuel blends, including fuel with a range of alcohol concentrations, such as various gasoline-ethanol blends, including E10, E85, gasoline, etc., and combinations thereof. A fuel level sensor106located in fuel tank20may provide an indication of the fuel level to controller12. As depicted, fuel level sensor106may comprise a float connected to a variable resistor. Alternatively, other types of fuel level sensors may be used.

Fuel pump21is configured to pressurize fuel delivered to the injectors of engine10, such as example injector66. While only a single injector66is shown, additional injectors are provided for each cylinder. It will be appreciated that fuel system18may be a return-less fuel system, a return fuel system, or various other types of fuel system. Vapors generated in fuel tank20may be routed to fuel vapor canister22, via conduit31, before being purged to the engine intake23.

Fuel vapor canister22is filled with an appropriate adsorbent for temporarily trapping fuel vapors (including vaporized hydrocarbons) generated during fuel tank refueling operations, as well as diurnal vapors. In one example, the adsorbent used is activated charcoal. When purging conditions are met, such as when the canister is saturated, vapors stored in fuel vapor canister22may be purged to engine intake23by opening canister purge valve162. While a single canister22is shown, it will be appreciated that fuel system18may include any number of canisters. In one example, canister purge valve162may be a solenoid valve wherein opening or closing of the valve is performed via actuation of a canister purge solenoid.

Canister22includes a vent27for routing gases out of the canister22to the atmosphere when storing, or trapping, fuel vapors from fuel tank20. Vent27may also allow fresh air to be drawn into fuel vapor canister22when purging stored fuel vapors to engine intake23via purge line28and purge valve162. While this example shows vent27communicating with fresh, unheated air, various modifications may also be used. Vent27may include a canister vent valve164to adjust a flow of air and vapors between canister22and the atmosphere. In one example, canister vent valve164may be a solenoid valve wherein opening or closing of the valve is performed via actuation of a canister vent solenoid.

One or more pressure sensors120may be coupled to fuel system18for providing an estimate of a fuel system pressure. One or more temperature sensors121may also be coupled to fuel system18for providing an estimate of a fuel system temperature.

Fuel system18may be operated by fuel pump electronics control module (PEM)156including a controller12receiving information from a plurality of sensors16included in the fuel system and sending control signals to a plurality of actuators81included in fuel system18. For example, the fuel system may be operated in an injection mode, wherein the controller12may activate fuel pump for providing a desired amount of fuel to a fuel rail for combustion.

Likewise, engine system8may be controlled at least partially by an engine control module (ECM)136including controller212receiving information from a plurality of sensors216(various examples of which are described herein) and sending control signals to a plurality of actuators281. As one example, sensors16may include TIP sensor, a humidity sensor, MAP sensor, and MCT sensor. As another example, actuators81may include fuel injector66, and intake throttle62. Other actuators, such as a variety of additional valves and throttles, may be coupled to various locations in engine system8. Controller212may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on instruction or code programmed therein corresponding to one or more routines.

Further, in some examples, PEM156and ECM136may each include a secondary diagnosis module for monitoring communication and detecting loss of communication from the PEM. Additionally or alternatively, communication monitoring and diagnosis from the PEM or ECM may be monitored by a diagnosis module (not shown) linked to a vehicle network (such as vehicle network110inFIG. 1). In some other examples, ECM may monitor communication from the PEM via a monitor line (not shown) linking the PEM and the ECM.

In one example, a loss of communication from the PEM may be detected. In response to the loss of communication, an estimated duration for vehicle failure under current operating conditions (in this example, the estimated duration before the vehicle stalls due to loss of torque resulting from loss of communication with the PEM) may be determined. Further, a diagnostic time threshold for setting loss of communication DTC may be determined based on the estimated duration for failure under current vehicle operating conditions. Upon a counter (that may be started in response to detecting the loss of communication) reaching the diagnostic time threshold, loss of communication DTC may be set. For example, the diagnostic time threshold may be less than the estimated duration for failure. In this way, loss of communication DTC may be set before the vehicle operation fails. As an example, if loss of communication from the PEM may stall the vehicle in 3 seconds at 70 miles per hour, then the diagnostic time threshold may be set to a value less than 3 seconds so as to activate the loss of communication DTC for PEM before the vehicle stalls.

Turning toFIG. 3, an example method300for setting a diagnostic code for loss of communication in a vehicle control system including a plurality of modules linked (e.g. control modules114shown inFIG. 1) to a vehicle data network (e.g. network110shown inFIG. 1). The method ofFIG. 3may be stored as executable instructions in non-transitory memory of each controller (e.g. controller112shown inFIG. 1) and carried out by the controller in combination with the various sensors, actuators, and engine and vehicle components illustrated inFIGS. 1-2. Additionally or alternatively, the method ofFIG. 3may be stored as executable instructions in non-transitory memory of a diagnostic controller included in a diagnostic module linked to a vehicle network (e.g. network110inFIG. 1).

At302, method300includes monitoring data from each of the plurality of modules in the vehicle network. In one example, a diagnostic module linked to the vehicle network may monitor one or more expected signals from each of the plurality of modules in the network. The expected signal may be transmitted from each of the plurality of modules in a predetermined format including a start of frame, an identifier, remote transmission request bit or substitute remote request bit, identifier extension, reserve bit, data length code, data, cyclic redundancy check, acknowledgement bit, end of frame, inter frame space, etc. In another example, the diagnostic module may monitor data in one or more monitor lines, each monitor line linking a module with the ECM. In still another example, the ECM may monitor the monitor line from each of the modules linked to the ECM via the monitor line(s). As such, the diagnostic module may be a centralized diagnostic module monitoring data from each of the plurality of the modules. In some examples, each module may include a secondary diagnostic module for monitoring data and diagnosing loss of communication. In some other examples, a hybrid approach may be utilized, wherein during some conditions, the centralized diagnostic module may be utilized and during some other conditions, the secondary diagnostic module(s) may be utilized. In yet another example, the centralized diagnostic module may be utilized to monitor signals from one or more groups of modules, each group including a number of individual modules comprising secondary diagnostic modules.

Next, at304, method300includes determining if loss of communication from any of the plurality of the modules is detected. Example methods for detecting loss of communication are further elaborated atFIGS. 4A-4B. In one example, loss of communication may be detected based on absence of the one or more expected signal for a first duration greater than a first threshold duration. In another example, loss of communication may be determined based on an error state of the monitor line(s) linking one or more modules to the ECM for a second duration greater than a second threshold duration. As such, the first and the second duration may be greater than a minimum duration, wherein the minimum duration may be the duration of reduced or dropped data activity, for example, during one or more of a vehicle power up mode, a module cycling operation through modes, and high vehicular network activity. If the answer at304is YES, then loss of communication is detected and accordingly, method300proceeds to305. If the answer at304is NO, then loss of communication is not detected and accordingly, method300returns.

At305, method300includes starting a counter (306) for activating loss of communication diagnostic trouble code (DTC). Further, a diagnostic time threshold (307) for activating the loss of communication DTC may be determined. The diagnostic time threshold may be based on an estimated duration for failure under given vehicle operating conditions due to loss of communication. Details of determining the diagnostic time threshold will be further elaborated atFIG. 5.

Next, at308, method300includes determining if a value of the counter is greater than or equal to the diagnostic time threshold. If the answer is YES, then the detected loss of communication may impact the performance of the vehicle (e.g., engine cooling, climate control, drivability, etc.), and accordingly method300proceeds to309. At309, method300includes activating the diagnostic time code (310) for loss of communication for the module from which loss of communication was detected. Further, method300includes resetting the counter (311). For example, upon detecting loss of communication from a fuel pump control module (PEM), and upon determining that the counter has reached the diagnostic time threshold, a U0109 DTC may be activated indicating lost communication with the fuel pump control module. Likewise, if loss of communication from a hybrid powertrain control module is detected and the counter reaches or exceeds the diagnostic time threshold, a U0293 DTC for lost communication with the hybrid powertrain control module may be activated. As such, the DTC may be readable by a universal diagnostic code reader of a kind known in the art. Further, in some examples, the loss of communication may be indicated to a vehicle operator. In one example, the indicator may be visual, e.g., an illuminated signal on a dashboard of the vehicle. In another example, the indicator may be audible.

Next, upon activating the loss of communication DTC, method300may proceed to318. At318, method300may include operating the vehicle in a failure mode.

Returning to308, if the counter is less than the diagnostic time threshold, method300may proceed to312. At312, method300includes determining if communication with the module is reestablished. For example, it may be determined that communication with the module is reestablished based on detecting the expected signal(s) from the module. In another example, it may be determined that communication with the module is reestablished based on the monitor line returning to a functional state from the error state. If the answer at312is YES, communication with the module is reestablished and accordingly, the loss of communication DTC may not be activated. If the answer at312is NO, the expected signal from the module is not detected and/or the monitor line remains in an error state. Therefore, upon not detecting normal communication from the module, method300may proceed to316. At316, the counter may be incremented. Upon incrementing the counter, method300may return to308to determine is the counter has reached or exceeded the diagnostic time threshold.

In this way, in response to detecting loss of communication, the loss of communication DTC may be activated such that the DTC is set prior to the vehicle entering a failure mode due to loss of communication from one or more control modules.

In one example, the method ofFIG. 3provides for a method for a vehicle, comprising: determining a first time threshold for a setting a loss of communication diagnostic trouble code based on an estimated duration for failure due to a loss of communication from a first control module connected to a vehicle network connecting a plurality of control modules in the vehicle. The method further includes in response to a counter exceeding the first time threshold, setting the loss of communication diagnostic trouble code, wherein the counter is started in response to determining the loss of communication from the first module.

The method further includes wherein the time threshold is less than the estimated duration for failure, and wherein the estimated duration of failure is based on one or more of a vehicle speed, a vehicle load condition, barometric pressure, and an operating condition of one or more vehicle components communicating with the first module at a time of detecting the loss of communication.

The method further includes wherein determining the loss of communication includes not detecting one or more expected signals from the first module, and wherein determining the loss of communication includes determining an error state of a monitor line communicating data between the first module and an engine control module (ECM) of the vehicle; and wherein the error state is determined based on the ECM not receiving data from the first module via the monitor line.

Further, the method comprises operating the vehicle in a failure mode in response to detecting the failure due to the loss of communication, and the method further includes wherein the loss of communication diagnostic trouble code is set prior to entering the failure mode.

Turning toFIG. 4A, an example method400afor detecting loss of communication from a control module linked to a vehicle network (e.g. network110shown inFIG. 1). As such, the control module may regulate one or more vehicle operations in a vehicle system including the vehicle network. The method ofFIG. 4may be stored as executable instructions in non-transitory memory of a controller (e.g. controller112shown inFIG. 1) and carried out by the controller in combination with the various sensors, actuators, engine and vehicle components illustrated inFIGS. 1-2. Additionally or alternatively, the method ofFIG. 3may be stored as executable instructions in non-transitory memory of a diagnostic controller included in a diagnostic module linked to a vehicle network (e.g. network110inFIG. 1).

At402, method400includes monitoring one or more expected signals from the control module. For example, a diagnostic module linked to the vehicle network may monitor the expected signal(s) from each module connected to the network. In some examples, a secondary module included in the control module may monitor the expected signal(s) from the control module. In some other examples, the expected signal(s) may be monitored by the diagnostic module and the secondary module. In still other examples, expected signal(s) from one or more control modules in the network may be monitored by the diagnostic module while the expected signal(s) from the remaining modules (that is, the modules that are not monitored by the diagnostic module) may be monitored by a secondary module included in each of the remaining modules. The expected signal may be transmitted from each of the plurality of modules in a predetermined format including a start of frame, an identifier, remote transmission request bit or substitute remote request bit, identifier extension, reserve bit, data length code, data, cyclic redundancy check, acknowledgement bit, end of frame, inter frame space, etc. Next at404, method400includes determining if the expected signal is detected. For example, the expected signal transmitted over the vehicle network may be detected by a module (such as the diagnostic module, the secondary module, ECM etc) monitoring the signal. If the answer is YES, method400may proceed to406to determine loss of communication not detected. If the answer at404is NO, then the expected signal is not detected and method400may proceed to408. At408, method400includes determining a duration of absence of the expected signal. In one example, a second counter may be started or incremented in response to not detecting the expected signal. The duration of absence of the expected signal may be determined based on the counter value.

Upon determining the duration of absence of the expected signal, method400may proceed to410. At410, method400may determine if the duration of absence is greater than a second threshold duration. If the answer at410is YES, method400may proceed to412. If the answer at410is NO, method400returns to step404. At412, upon confirming that the duration of absence is greater than the second threshold duration, method400may infer loss of communication from the module. That is, upon confirming that the expected signal loss has occurred for a duration greater than the second threshold, method400may determine that the control module has lost communication with the vehicle network.

Turning toFIG. 4B, an example method400bfor detecting loss of communication from a control module linked to a vehicle network (e.g. network110shown inFIG. 1). As such, the control module may regulate one or more vehicle operations in a vehicle system including the vehicle network. The method ofFIG. 4may be stored as executable instructions in non-transitory memory of a controller (e.g. controller112shown inFIG. 1) and carried out by the controller in combination with the various sensors, actuators, engine and vehicle components illustrated inFIGS. 1-2. Additionally or alternatively, the method ofFIG. 3may be stored as executable instructions in non-transitory memory of a diagnostic controller included in a diagnostic module linked to a vehicle network (e.g. network110inFIG. 1).

At414, method400includes monitoring a monitor line connecting the control module with the ECM. The monitor line may include diagnostic data for determining functional communication from the control module. In one example, the monitor line may be monitored by a diagnostic module linked to the vehicle network. In another example, a secondary module included in the control module may monitor the monitor line. In still another example, the ECM may monitor the monitor line. In some other examples, the monitor line may be monitored by a combination of two or more of the diagnostic module, the secondary module, and the ECM. In still other examples, one or more control modules in the network may be monitored by the diagnostic module while the remaining modules (that is, the modules that are not monitored by the diagnostic module) may be monitored by a secondary module included in each of the remaining modules and/or the ECM.

Next at416, method400includes determining if an error state of the monitor line is detected. For example, the error state may be detected by a module (such as the diagnostic module, the secondary module, ECM, etc.) monitoring the signal. Further, the error state may be determined based on absence of one or more signals in the monitor line. In some examples, the error state may be determined based on presence of truncated or altered signal in the monitor line. If the answer is NO, method400may proceed to417to determine loss of communication not detected. If the answer at404is YES, then the monitor line is operating in an error state and accordingly, method400may proceed to418. At418, method400includes determining a duration of error state. In one example, an error state counter may be started or incremented in response to determining operation of the monitor line in the error state. The duration of error state may be determined based on the counter value.

Upon determining the duration of error state of the monitor line, method400may proceed to420. At420, method400may determine if the duration of error state is greater than an error state threshold duration. If the answer at420is YES, method400may proceed to422. If the answer at420is NO, method400returns to step416. At420, upon confirming that the duration of error state is greater than the error state threshold duration, method400may infer loss of communication from the module. That is, upon confirming that the monitor line has remained in the error state for a duration greater than the error state threshold, method400may determine that the control module has lost communication with the vehicle network.

In this way, communication from the plurality of modules in the vehicle network may be monitored and loss of communication from the modules may be detected.

Turning toFIG. 5, a method500for determining a diagnostic time threshold is shown. The diagnostic time threshold may be utilized for setting a loss of communication diagnostic time code. For example, in response to detecting loss of communication from a control module linked to a vehicle network for a duration greater than the diagnostic time threshold, the loss of communication DTC may be set. In other words, intelligent decisions for setting loss of communication DTCs may be based on the diagnostic time threshold. The method ofFIG. 5may be stored as executable instructions in non-transitory memory of a controller (e.g. controller112shown inFIG. 1) and carried out by the controller in combination with the various sensors, actuators, engine and vehicle components illustrated inFIGS. 1-2.

Next, at504, method500includes determining the diagnostic time threshold for setting a loss of communication DTC under current vehicle operating conditions based on a calibratable look-up table. The calibratable look-up table may be generated based on current operating conditions, and further based on an estimated duration for failure of vehicle operation or operator perceivable degradation of vehicle performance to occur due to the loss of communication. That is, the diagnostic time threshold may be based on the estimated duration for failure and/or vehicle performance degradation to occur under current operating conditions due to loss of communication from the module. The estimated duration of failure and/or duration for vehicle performance degradation may be based on one or more of a vehicle speed, a vehicle load condition, barometric pressure, and an operating condition of one or more vehicle components communicating with the module (at which the loss of communication is detected) at a time of detecting the loss of communication. In one example, the diagnostic time threshold may be less than the duration for failure due to loss of communication.

In one example, when communication from a fuel pump electronics control module (PEM) is lost, the diagnostic time threshold for loss of communication from the PEM may be based on an estimated duration of engine operation before the vehicle stalls due to lack of fuel (and hence, lack of torque) under current vehicle operating conditions. For example, the estimated duration for failure (that is, duration before stalling) under high load operating conditions (e.g. vehicle operation on an expressway, during towing heavy loads, etc.) may be shorter than the estimated duration for failure under light load operating conditions. Consequently, the diagnostic time threshold for loss of communication DTC for PEM under high load operating conditions may be shorter than the diagnostic time threshold for loss of communication DTC for PEM under light load operating conditions. For example, in response to loss of communication from the PEM, if the estimated duration for failure (that is, the estimated duration for stalling) is three seconds at seventy miles per hour, the diagnostic time threshold may be less than three seconds. As a result, the loss of communication DTC for the PEM may be set before the vehicle stalls, thereby allowing the PEM loss of communication to be detected.

In another example, the diagnostic time threshold for setting loss of communication DTC for loss of communication from an engine coolant pump control module may be based on an estimated duration for degraded vehicle performance in terms of engine cooling, climate control, and drivability under current vehicle operating conditions.

In this way, by determining the diagnostic time threshold based on an estimated duration for failure due to loss of communication under current vehicle operating conditions, the loss of communication DTC may be set prior to the vehicle failing. By setting the loss of communication DTC prior to the failure of vehicle operation, the cause of vehicle failure (in this case, loss of communication from the control module) may be determined.

FIG. 6shows operating sequence600depicting an example activation of a loss of communication diagnostic code in response to detection of loss of communication from a control module in a vehicle network such as the vehicle network110atFIG. 1.FIG. 6illustrates example pedal position at plot602, state of vehicle function at plot604, counter one for setting loss of communication diagnostic trouble code at plot606, and failure mode at plot608. The sequence of events inFIG. 6may be provided by executing instructions in the system ofFIGS. 1-2according to the method ofFIG. 3-5. Vertical markers at times t0-t3represent times of interest during the sequence. In all the plots discussed below, the X axis represents time and time increases from the left side of each plot to the right side of each plot.

The first plot from the top ofFIG. 6represents loss of communication versus time. The Y axis represents loss of communication. Level zero represents absence of detected loss of communication and level one represents presence of detected loss of communication.

The second plot from the top ofFIG. 6represents a state of vehicle function versus time. The Y axis represents a failed or a normal state of vehicle function.

The third plot from the top ofFIG. 6represents a value of a first counter one versus time. The Y axis represents the value of the counter one and the value increases in the direction of the Y axis arrow. Horizontal line605represents a diagnostic time threshold for setting a loss of communication diagnostic trouble code for the control module. The diagnostic time threshold may be based on current vehicle operating conditions, and an estimated duration for failure due to loss of communication from the control module.

The fourth plot from the top ofFIG. 6represents a state of a failure mode of the vehicle versus time. The Y axis represents the state of the failure mode.

At times between t0and t1, loss of communication from a control module in the vehicle network may not be detected. Accordingly, vehicle may be operating as expected (that is, normal vehicle operation without loss of communication or loss of function), and counter one for setting loss of communication DTC may be at zero.

At t1, a loss of communication from the control module may be detected. In one example, loss of communication may be determined based on absence of one or more expected signal(s) from the control module. In another example, loss of communication may be based on determination of an error state of a diagnostic monitor line linking the control module with the ECM. Details of determining loss of communication is elaborated atFIGS. 4A-4B. Upon detecting the loss of communication from the module, counter one may be started. Further diagnostic time threshold605may be adjusted based on an estimated time for failure of vehicle operation or degradation of vehicle operation due to the loss of communication under current operating conditions. For example, if a loss of communication from a PEM is detected and the vehicle is operating under high load conditions, the diagnostic time threshold may be based on an estimated duration for vehicle to stall (due to lack of torque resulting from lack of fuel due to lost communication with PEM) under the high load conditions. If the loss of communication from the PEM is detected when the vehicle is operating under low load conditions, the diagnostic time threshold may be based on an estimated duration for vehicle to stall (due to lack of torque resulting from lack of fuel due to lost communication with PEM) under the low load conditions. As such, the diagnostic time threshold may be less than the estimated duration for vehicle failure due to loss of communication so as to set the loss of communication DTC prior to occurrence of vehicle failure due to the loss of communication from the module.

At times between t1and t2, the communication from the PEM may not be restored and consequently, counter one may continue to increase. At t2, the counter may reach the diagnostic time threshold for activating the loss of communication DTC. Upon counter one reaching the diagnostic time threshold, the DTC for loss of communication may be activated. For example, in response to a counter for loss of communication from a PEM reaching a PEM diagnostic threshold under current operating conditions, the loss of communication DTC for PEM (e.g. U0109) may be activated. Similarly, in response to a counter for loss of communication from a cruise control module (ICCM) reaching an ICCM diagnostic threshold under current operating conditions, the loss of communication DTC for ICCM (e.g. U0104) may be activated.

At t3, vehicle may enter a state of failure due to loss of communication from the module. Consequently, the DTC for failed vehicle function may be activated and the vehicle may be operated in a failure mode. For example, due to loss of communication from the PEM, a difference between a demanded torque and an actual torque may be greater than a threshold torque difference. As a result, DTC related to loss of torque may be activated. While the above example illustrates entering a failure mode in response to detecting a vehicle function failure, in some examples, the vehicle may be operated in the failure mode upon activating the loss of communication DTC. That is, vehicle may be operated in the failure mode at t2instead of t3.

In this way, vehicle systems may be equipped with intelligent loss of communication detection feature wherein a threshold for activating loss of communication DTC is determined based on an estimated duration for failure due to loss of communication under current operating conditions such that the loss of communication DTC is set prior to the vehicle entering a failure mode of operation. As a result, vehicle loss of communication diagnostics may be improved. In one example, a method for loss of communication in a control system of a vehicle may comprise: in response to determining a loss of communication from a first module coupled to a controller area network of the control system, starting a first counter; and setting a loss of communication diagnostic time code in response to the first counter exceeding a first diagnostic time threshold; and wherein, the first diagnostic time threshold is less than an estimated duration for occurrence of a failure due to the loss of communication.

The method includes wherein the estimated duration for failure is an output of a calibratable look up table utilizing as inputs one or more of a vehicle speed, a desired load, a barometric pressure, an ambient temperature, and an operating condition of one or more vehicle components communicating with the first module at a time of determination of the loss of communication. In some examples, the method includes wherein the loss of communication is determined based on not detecting one or more signals in a monitor line between the first module and an engine control module for a second time threshold.

Further, the method comprises operating the vehicle in a failure mode in response to setting the loss of communication diagnostic code. Still further, the method includes wherein the first module is a pump electronic module (PEM); and wherein the PEM regulates operation of a fuel pump located in a fuel tank of the vehicle, and wherein the failure is a difference between a desired torque output and a current torque output greater than a threshold torque output.

Further, the method includes operating the vehicle in a failure mode in response to detecting loss of communication from the PEM.