Control method and apparatus for diagnosing vehicles

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said step of sensing operating parameters includes detection of an engine misfire in a combustion cylinder of said vehicle, wherein control of an accidental or improper fire has priority over control of malfunctions of other subsystems of said vehicle;
• wherein said step of sensing operating parameters includes sensing engine speed and engine load of said vehicle;
• and further comprising
• additional steps wherein if a misfire is detected when said engine speed is in an idling range or said engine load is smaller than a predetermined value, a first check is made to detect ignition abnormalities in said vehicle and if such an abnormality is detected, to correct such abnormality by increasing magnitude and duration of an ignition current provided to said combustion cylinder;
• an additional step wherein if a misfire is detected when said engine load is greater than said predetermined value, fuel supply to said combustion cylinder is interrupted for a predetermined period of time and then resumed;
• an additional step wherein if said misfire continues after interruption of said fuel supply, magnitude and duration of an ignition current provided to said combustion cylinder are increased;
• an additional step wherein if said misfire is not corrected, fuel supply to said combustion cylinder is stopped;
• and
• the further step of modifying operation of other combustion cylinders firing before and after said combustion cylinder in which said misfire is detected, by one of:
• decreasing fuel flow or retarding ignition timing to said other cylinders.

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said subsystems include at least one of:
• cylinder ignition, exhaust catalyst, O.sub.2 sensors, O.sub.2 sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;
• and
• wherein said step of sensing operating parameters includes sensing one of engine intake air flow and engine exhaust gas temperature;
• and comprising the following additional steps
• an air fuel ratio of said engine of said vehicle is controlled by an air-fuel feedback signal having a periodic cycle;
• and
• if a malfunction of said exhaust catalyst is detected when said sensed one of engine intake air flow and engine exhaust gas temperature is smaller than a predetermined value, said cycle of said air-fuel feedback signal is shortened.

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said subsystems include at least one of:
• cylinder ignition, exhaust catalyst, O.sub.2 sensors, O.sub.2 sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;
• wherein said vehicle has an air-fuel ratio feedback control system responsive to an O.sub.2 sensor located upstream of said exhaust catalyst;
• and
• wherein said step of sensing operating parameters includes:
• sensing a degradation index of said O.sub.2 sensor located upstream of said exhaust catalyst;
• comparing said degradation index to a first predetermined value;
• if said degradation index is less than said first predetermined value, changing a gain of said air-fuel ratio feedback control system in response to magnitude of said degradation index.

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said subsystems include at least one of:
• cylinder ignition, exhaust catalyst, O.sub.2 sensors, O.sub.2 sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;
• wherein said vehicle has an air-fuel ratio control system responsive to output signals from an O.sub.2 sensor in an exhaust line thereof, which control system can use either of a feedback (closed loop) control process or an open loop control process, said step of sensing operating parameters includes sensing heater current of said O.sub.2 sensor to detect an abnormal condition thereof;
• and
• wherein said sequence of corrective measures comprises the steps of:
• comparing at least one of intake air flow and exhaust gas temperature of said vehicle with a first preset value;
• and
• if it is less than said preset value, air-fuel ratio feedback control responsive to output signals from said O.sub.2 sensor is stopped.

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said subsystems include at least one of:
• cylinder ignition, exhaust catalyst, O.sub.2 sensors, O.sub.2 sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;
• wherein said vehicle has an air-fuel ratio control system which can use either a feedback (closed loop) learning control process or an open loop control process;
• and
• wherein said step of sensing operating parameters comprises sensing pressure of said evaporative fuel system to detect an evaporative fuel leak;
• and comprising an additional step wherein if said evaporative fuel leak exceeds a predetermined value, learning control of said air-fuel ratio control system is stopped.

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said subsystems include at least one of:
• cylinder ignition, exhaust catalyst, O.sub.2 sensors, O.sub.2 sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;
• wherein said step of sensing operating parameters comprises sensing intake air pressure of said vehicle to detect exhaust gas recirculation flow of said exhaust gas recirculation valve;
• and
• wherein said sequence of corrective measures comprises the steps of:
• comparing exhaust gas recirculation flow with a first predetermined value;
• if it exceeds said predetermined value, checking for new air leaks;
• and
• if no new air leak is found, adjusting said air-fuel ratio to make it richer.

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said subsystems include at least one of:
• cylinder ignition, exhaust catalyst, O.sub.2 sensors, O.sub.2 sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;
• wherein said vehicle has an air-fuel ratio control system which utilizes a feedback control process;
• wherein said step of sensing operating parameters includes sensing output characteristics of an O.sub.2 sensor downstream of a secondary air outlet of said vehicle to detect and evaluate an abnormality of an air shut off valve of said secondary air supply;
• and
• wherein said sequence of corrective measures comprises the step of
• if said air shut off valve is determined to be frozen in an open position, stopping feedback control of said air-fuel ratio control system.

Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

• providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;
• sensing operating parameters of each of said subsystems and providing output signals indicative thereof;
• processing said output signals in a data processor to detect a malfunction at least one of said subsystems;
• selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;
• sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor;
• and
• testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;
• wherein said system is a vehicle having an internal combustion engine;
• wherein said subsystems include at least one of:
• cylinder ignition, exhaust catalyst, O.sub.2 sensors, O.sub.2 sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;
• and
• wherein if a malfunction is detected in said fuel control system, said sequence of corrective measures includes the steps of
• comparing throttle valve opening of said vehicle with output signals of a hot wire of an air flow sensor in said fuel control system to detect a malfunction of said air flow sensor;
• if a malfunction of said air flow sensor is detected, estimating air flow based on throttle valve opening and engine speed.