unitEngineElectronicControl汽车实用英语.pptx
Unit 4 Engine Electronic Control Systems Service第1页/共113页Upon completion of this unit,you should be able to:Overall Objectives Learn key terms about engine electronic control systems in this unit.Understand the process of inspection and repair of engine electronic control systems.Use maintenance manual to deal with the practical problems.第2页/共113页Task 4.1 Engine Control System Inspection-发动机控制系统检测Task 4.2 Fuel Injector Replacement-更换喷油器Task 4.3 Emission Control Inspection-排放控制检测Task 4.4 Ignition System Inspection-点火系统检测Task 4.5 Diagnostic Procedures-诊断程序Tasks Introduction 第3页/共113页 Automotive engine control systems must satisfy diverse and often conflicting requirements.Servicing these systems regularly ensures the automotive running normally and meeting stringent standards.The following tasks(e.g.engine control system inspection,fuel injector replacement,ignition system inspection,etc.)are the important items in engine electronic system servicing to control exhaust emissions,fuel economy and other performance indicators of the engine.Task Description 第4页/共113页Task 4.1 Engine Control System Inspection第5页/共113页Learning Preparation engine electronic system intake air flow meterohmmeterresistanceterminalvoltmeterpositivenegativethrottle position sensorknock sensorKey terms:发动机电控系统进气空气流量计欧姆表电阻终端，端子伏特计，电压表正极负极节气门位置传感器爆震传感器第6页/共113页Step 1 A maintenance case is provided;Step 2 Learn the process of inspecting the engine electronic system;Step 3 Require students to grasp the key terms in this task;Step 4 Try to describe the process of inspecting the engine electronic system;Step 5 Students read relative material;Step 6 AssessmentPlan and Implement 第7页/共113页()1.The resistance of the intake air flow meter is related to the temperature.()2.When inspecting the voltage of terminal VG and E2G,you should turn off the ignition switch.()3.If air is blown into the intake air flow meter,the voltage should change with the air flow.()4.If the resistance of the camshaft timing oil control valve is 7.3,it is ok.()5.When testing the movement of the camshaft timing oil control valve,terminal 2 should be connected with the positive lead of the battery.Assessment and Feedback True or False 第8页/共113页()6.The bad returning the valve may be caused by entrance of foreign objects.()7.There is a clearance between the throttle stop screw and throttle lever at the throttle closed position.()8.In the inspection of the throttle position sensor,the resistance between terminals VTA and E2 should change in proportion to the throttle lever opening value.()9.The water temperature sensor can not be checked in the water.()10.If the resistance of the knock control sensor is 50k at 20C,it should be changed.第9页/共113页 An Air Flow Sensor（空气流量传感器）or Mass Air flow Sensor(MAF)is one of the components of an electronic fuel injection system of a modern car or truck.A mass air flow sensor is installed inside the intake air duct between the air cleaner and the intake manifold of the engine.A mass air flow sensor measures the amount of air entering the engine.Often an intake air temperature sensor(IAT)is also installed within the mass air flow sensor.There are few types of air flow sensors,however a hot-wire type is used the most in the modern cars.Lets see how it works.A hot-wire mass air flow sensor（热线式空气流量计）has a small electrically heated wire(hot wire)and a small temperature sensor installed close to the hot wire.The temperature sensor measures the temperature of the air near the hot wire.4.1.1 What is a Mass Air Flow Sensor(MAF)第10页/共113页 Fig4.1.1 Mass Airflow Sensor(MAF)Fig.4.1.2 Location of the MAF Fig4.1.3 Toyota mass airflow sensor(MAF)Fig4.1.4Volkswagen mass airflow sensor第11页/共113页 When the engine is idling,a very little air flows pass the hot wire,so it takes very small electrical current to keep the wire hot.When you press the gas,the throttle opens allowing more air to flow over the hot wire.The passing air cools the hot wire down;the more air flows over the wire,the more electrical current（电流）is needed to keep it hot.The amount of this electrical current is proportional to the amount of the air flow.第12页/共113页 A small electronic chip installed inside the airflow sensor turns the amount of this electrical current into a digital signal that is sent to the engine computer(ECM).The computer uses the air flow signal（信号）to calculate the proper amount of fuel injected into the cylinders in order to keep an optimal air/fuel ratio.This is needed to keep the exhaust emissions low without sacrificing the engine performance.In addition,the computer uses the air flow readings to determine the shift points of the automatic transmission（自动变速器）;so if the air flow sensor doesnt work properly,the automatic transmission might shift gears differently.第13页/共113页 Problems of mass air flow sensors are very common.The air flow sensor usually gets contaminated or damaged when a bad or improperly installed air filter allows some unfiltered（未经过滤的）air into the engine or when oil from an oil-soaked air filter contaminates the air flow sensor.A bad or contaminated mass air flow sensor cannot measure the amount of air flow correctly.This can cause various driveability problems such as stalling,especially when the engine is cold,misfiring,lack of power,poor acceleration,etc.In addition,a problem with the mass air flow sensor will cause the Check engine or Service engine light to come on.4.1.2 Mass Air Flow Sensor Problems 第14页/共113页 The“check engine”light comes on when the computer has detected a fault in one of the engine electronic systems.This fault（故障）is stored as a trouble code and can be retrieved from the computer with a scan tool.The following trouble codes are associated with a mass airflow sensor:P0100-Mass Air Flow Circuit MalfunctionP0101-Mass Air Flow Circuit Range/PerformanceP0102-Mass Air Flow Circuit LowP0103-Mass Air Flow Circuit HighP0104-Mass Air Flow Circuit Intermittent The trouble codes P0171 System Too Lean(Bank 1)and P0174 System Too Lean(Bank 2)are also could be caused by a bad or contaminated mass air flow sensor.If your check engine light is on,have your vehicles computer scanned and read more about lean codes.第15页/共113页 Often,an air flow sensor can be checked with a scan tool.Usually,the air flow readings of the sensor in question is compared to the readings of a known good sensor.Typically,a contaminated air flow sensor will show different amount from a known good sensor.If the air flow sensor is bad,it will need to be replaced.Its a fairly simple job,however the air flow sensor itself could cost up to a few hundred dollars.If the sensor is just dirty,your mechanic may suggest cleaning it(cleaning the airflow sensor is a delicate procedure)as a temporary solution sometimes this could help you.If the new mass air flow sensor is installed,make sure the air filter is installed properly,as the sand particles coming with the unfiltered air can damage the air flow sensor.第16页/共113页Practice Maintenance Manual Reading 1.Intake air flow meter SUB-ASSY.(a)Inspect the intake air flow meter resistance.(1)Using an ohmmeter,measure（测量）the resistance between terminals THA and E2.Engine Control System Inspection第17页/共113页HINT:If the resistance is not as specified,replace the intake air flow meter.(b)Inspect the intake air flow meter operation.(1)Connect the intake air flow meter connector.(2)Turn the ignition switch（点火开关）to ON.(3)Using a voltmeter,connect the positive(+)tester probe to terminal VG,and negative()tester probe to terminal E2G.(4)Blow air into the intake air flow meter,and check that the voltage fluctuates.第18页/共113页 HINT:If operation is not as specified,replace the intake air flow meter.(5)Turn the ignition switch to LOCK.(6)Disconnect the intake air flow meter connector.第19页/共113页2.Camshaft timing oil control valve ASSY(a)Resistance inspection.(1)Using an ohmmeter,measure the resistance between the terminals.Resistance:6.9 to 7.9 at 20C(68F)(b)Movement inspection.(1)Connect the positive(+)lead from the battery（蓄电池）to terminal 1 and negative()lead to terminal 2,and check the movement of the valve.NOTICE:Confirm the valve does not adhere.HINT:Bad returning of the valve（阀）by entrance of foreign objects causes subtle pressure leak to the advanced direction.Then,DTC can be detected.第20页/共113页 3.Throttle body ASSY(a)Check throttle body.(1)Check that throttle valve shaft is not rickety.(2)Check that each port is not stopped up（堵塞）.(3)Check that throttle valve opens and closes smoothly.(4)Check that there is no clearance between the throttle stop screw and throttle lever at the throttle closed position.NOTICE:Do not adjust the throttle stop screw.第21页/共113页4.E.F.I.Throttle Position Sensor(a)Resistance inspection.(1)Disconnect the throttle position sensor connector.(2)Using an ohmmeter,measure the resistance between terminals VC and E2.Resistance:2.5 to 6.0 k(3)Check the change of resistance between terminals VTA and E2.Change of resistance:The resistance value（电阻值）increases in proportion to the throttle lever opening value.第22页/共113页第23页/共113页5.E.F.I.Engine Coolant Temperature Sensor(a)Resistance inspection.(1)Using an ohmmeter,measure the resistance between each terminal.Resistance:At 20C(68F)2.32 2.59 kAt 80C(176F)0.310 0.326 kNOTICE:In case of checking the water temperature sensor（水温传感器）in the water,be careful not to allowwater to go into the terminals,and after checking,wipe out the sensor.第24页/共113页6.Knock Control Sensor(a)Using an ohmmeter,measure the resistance between terminals.Resistance:120 280 k at 20C(68F)HINT:If the resistance is not specified,replace the sensor.HINT:If the resistance is not specified,replace the sensor.第25页/共113页7.E.F.I.Circuit Opening Relay（继电器）ASSY(a)Continuity inspection.(1)Using an ohmmeter,check that continuity exists between each terminal.Specified condition:Between terminals 1 and 2 ContinuityBetween terminals 3 and 5 No continuity(2)Using an ohmmeter,check that continuity exists between terminals 3 and 5 when he battery voltage is applied across terminals 1 and 2.第26页/共113页Task 4.2 Fuel Injector Replacement第27页/共113页Learning Preparation fuel injector cylinder head coverventilation hoseretainerconnectorinsertfuel delivery pipetwistKey terms:喷油器汽缸盖罩通风软管保持架接头，连接器插入燃油分配管扭转，扭曲第28页/共113页Step 1 A maintenance case is provided;Step 2 Learn the process of replacing fuel injector via a maintenance manual;Step 3 Require students to grasp the key terms in this task;Step 4 Try to describe the process of replacing fuel injector;Step 5 Students read relative material;Step 6 AssessmentPlan and Implement 第29页/共113页()1.When you replacing the injectors,you must prevent the gasoline leakage.()2.The ventilation hose is connected with the cylinder block.()3.The engine is a type of multi-point fuel injection.()4.The harness clamps are used to fix the wires.()5.An SST must be adopted to disconnect the fuel tube.Assessment and Feedback True or False 第30页/共113页()6.The pipe and the connector should be kept very clean.()7.The fuel injectors should be removed with the fuel delivery pipe.()8.The insulator installed on each fuel injector needs not to be changed.()9.When installing the injector to the fuel delivery,you can apply a little engine oil on the O-ring.()10.The injector should be pushed directly to the fuel delivery pipe.第31页/共113页 The EFI(Electronic Fuel Injection)system（电控燃油喷射系统）uses sensors to detect the engine condition and vehicle running condition.And the engine ECU（电控单元）calculates the optimum fuel injection volume,and causes the injectors to inject the fuel.Fig.4.2.1 shows the basic EFI configuration.4.2.1 Electronic Fuel Injection System第32页/共113页Fig.4.2.1 Electronic Fuel Injection System1-exhaust gas oxygen sensor;2-injector;3-fuel pressure regulator;4-coolant temperature sensor;5-idle control valve;6-air flow meter;7-fuel tank;8-fuel pump;9-fuel filter;10-ECU 第33页/共113页The Electronic Fuel Injection system can be divided into three basic subsystems:the fuel delivery system,the air induction system and the electronic control system.The fuel delivery system consists of the fuel tank（油箱）,fuel pump,fuel filter,fuel delivery pipe(fuel rail),fuel injector,fuel pressure regulator,and fuel return pipe.Some engines also have pulsation damper.The fuel is taken from the fuel tank by the fuel pump and sprayed under pressure by an injector.The fuel pressure in the fuel line must be regulated to maintain stable fuel injection by the pressure regulator.Any fuel which is not delivered to the intake manifold by the injector（喷油器）is returned to the tank through a fuel return pipe.第34页/共113页The air induction（空气供给）system consists of the air cleaner,air flow meter,throttle valve,air intake chamber,intake manifold runner,and intake valve.When the throttle valve is opened,air flows through the air cleaner,through the air flow meter,past the throttle valve,and through a well tuned intake manifold runner to the intake valve.Air delivered to the engine is a function of driver demand.As the throttle valve is opened further,more air is allowed to enter the engine cylinder.The electronic control system consists of various engine sensors,Electronic Control Unit(ECU),various actuators.There are many sensors such as mass airflow sensor,manifold absolute pressure sensor,throttle position sensor,engine coolant temperature sensor,intake air temperature sensor,crankshaft position sensor,camshaft position sensor,and exhaust gas oxygen sensor,etc.第35页/共113页The basic function of the ECU is to control the pulse width of the injector.In engine management systems,the ECU controls additional functions,such as idle speed（怠 速）,ignition timing,and fuel pump operation.The actuators（执行元件）contain fuel pump relay,injector,Malfunction Indicator Light(MIL),EVAP canister purge solenoid valve,air conditioner relay,cooling fan relays,idle control valve,etc.Air enters the engine through the air induction system where it is measured by the air flow meter.As the air flows into the cylinder,fuel is mixed into the air by the fuel injector.Fuel injectors are arranged in the intake manifold behind each intake valve.The injectors are electrical solenoids which are operated by the ECU.The ECU pulses the injector by switching the injector ground circuit on and off.第36页/共113页When the injector is turned on,it opens,spraying atomized fuel at the back side of the intake valve.As fuel is sprayed into the intake airstreams,it mixes with the incoming air and vaporizes due to the low pressure in the intake manifold.The ECU signals the injector to deliver just enough fuel to achieve an ideal air/fuel ratio（空 燃 比）of 14.7:1,often referred to as stoichiometry.The precise amount of fuel delivered to the engine is a function of ECU control.The ECU determines the basic injection quantity based upon measured intake air volume and engine rpm（转速）.Depending on engine operating conditions,injection quantity will vary.The ECU monitors variables such as coolant temperature,engine speed,throttle angle and exhaust oxygen content
