Automobile Inspection Technology

Chapter 20 Detection Technology of Automotive Electronic Control System (5)
桑塔纳2000Gsi、3000型轿车的进气温度传感器G72安装在进气歧管上。传感器插座上有两个接线端子，信号输出端子与电控单元J220插座上的端子54连接，传感器的负极与电控单元J220插座上的传感器搭铁端子67连接，如图4-37所示。将万用表的两只表笔分别连接传感器插座上的信号输出端子与传感器搭铁端子，测得标准电阻应当如表4-7所示。

[-]. Detection of actuator

Checking and troubleshooting the automotive electronic control system is mainly to repair wiring harnesses, components and connectors.The actuator is the actuator of various electronic control systems. Once the actuator fails, it will not be able to perform normal work, and the control system will lose its normal control function.The maintenance methods of various actuators are different, and the maintenance methods of several typical actuators are introduced below.

1. Maintenance of electric fuel pump

(1) Use of electric fuel pump
When the electric fuel pump is in use, the following two points must be paid attention to:

① The old oil pump cannot be tested dry.After the oil pump is disassembled, because there is gasoline remaining in the pump casing, during the power-on test, once the contact between the brush and the commutator is poor, sparks will be generated to ignite the gasoline in the pump casing and cause an explosion. The consequences are disastrous.

② The new oil pump cannot be tested dry.Since the oil pump motor is sealed in the pump casing, the heat generated by power-on during the dry test cannot be dissipated, and the motor will burn out if the armature is overheated. Therefore, the oil pump must be immersed in gasoline for testing.

(2) Maintenance of electric fuel pump

The maintenance methods of fuel pumps of various fuel injection systems are basically the same.When the electric fuel pump of the electronic control system fails, the engine ECU cannot detect the fault information, nor can it be read by the VA, G1552 or VAG1551 fault reader

accident details.When the battery voltage is normal and the fuse of the fuel pump is also normal, turn on the ignition switch, and the sound of the fuel pump starting and working for about 2 seconds should be heard near the fuel tank at the rear of the car.

The fuel pump, hot-film air flow sensor, activated carbon tank solenoid valve, and oxygen sensor heating element of the electronic control system of Santana 2000GSi are all controlled by the fuel pump relay.When the ignition switch is turned on, if the sound of the fuel pump running cannot be heard, turn off the ignition switch, check the fuel pump relay at the No. 2 position of the central relay box and the fuel pump fuse S5 (No. 5 position of the fuse box, 10A) Is it good.If the fuel pump fuse is good, insert the fuel pump fuse, then unplug the fuel pump relay from the central circuit board, and use a multimeter to detect the low voltage between terminal 4/86 on the relay socket and ground terminal 31, standard The voltage should be equal to the battery voltage (around 2V).

When checking the fuel delivery rate of the fuel pump, turn off the ignition switch, remove the fuel inlet pipe from the fuel distribution pipe, connect the oil pressure gauge to one end of the fuel pipe, extend the oil pressure gauge outlet pipe to the measuring bottle, and connect the fuel pump circuit (plug the battery The positive electrode is added to the fuel pump relay terminal) for 30s, the relationship between the pump oil volume and the power supply voltage is shown in Figure 4-38(b), and the unit is ml/30s.

When the battery voltage is 10-12V and the oil pressure is 300kPa, the pump oil volume should be 490-670ml.It can be seen that the higher the system oil pressure, the greater the pump oil volume; the higher the oil pump power supply voltage, the higher the oil pump speed, and the greater the pump oil volume.If the oil pressure is too high, replace the oil pressure regulator; if the oil pressure is too low, check whether the oil pipe is bent, whether the oil circuit or gasoline filter is blocked.

2. Maintenance of oil pressure regulator

The inspection of the oil pressure regulator of the fuel injection system includes the inspection of the fuel supply pressure and the pressure holding capacity.

(1) Check the oil supply pressure

In order to ensure that the fuel supply system can supply a sufficient amount of fuel under various working conditions of the engine, the actual fuel pressure supplied by the fuel supply system is not a fixed value under different working conditions.Specific regulations for Santana GLi, 2000GLi and 2000GSi cars are shown in Table 4-8.

When the power supply voltage is normal, connect the oil pressure gauge to the oil inlet of the fuel distribution pipe. When the engine is started and idling, the pressure rating of the oil pressure gauge is 300kPa±20kPa; The pressure should increase rapidly to about 320kPa; when the vacuum tube on the oil pressure regulator is unplugged, the pressure of the oil pressure gauge must rise to 320kPa.If the oil pressure does not meet the above requirements, it means that the oil supply system is faulty and should be overhauled or replaced.The cause of excessive oil pressure is that the oil pressure regulator is damaged and should be replaced with a new one.The cause of the low oil pressure regulator is oil leakage from the oil pipe joint or oil pipe, clogged fuel filter, low battery voltage or damage to the oil pressure regulator.

(2) Check the pressure holding capacity

When the power supply voltage is normal, start the engine and run it at idle speed. After the pressure of the oil pressure gauge reaches the above rated value, turn off the ignition switch and wait for 10 minutes. The pressure of the oil pressure gauge must be higher than 200kPa.If it is lower than 200kPa, start the engine again and run at idle speed to make the pressure reach the rated value, disconnect the ignition switch, and clamp the oil return pipe with pliers, and observe the pressure of the oil pressure gauge at the same time. After waiting for 10 minutes, if the oil pressure gauge is higher than 200kPa, Indicates that the oil pressure regulator is invalid and should be replaced.If the gauge pressure is lower than 200kPa, it means that there is leakage in the fuel delivery pipe and fuel injector, or the check valve of the fuel pump is faulty, or the O-ring seal at the inlet of the fuel injector is invalid, and repairs are required item by item.When unplugging the fuel injector to check its oil leakage, under the condition of normal oil pressure gauge, the oil drop should not exceed 0 drops per minute.

3. Maintenance of electromagnetic injector

When the fuel injector is clogged, dripping oil and other faults, the engine ECU cannot detect it, and the fault information of the fuel injector cannot be read by using the fault reader.Inspection and maintenance of fuel injectors can be judged by detecting its resistance and voltage.

(1) Detect the resistance of the electromagnetic injector

Use the multimeter 0HM2000 to detect the resistance value of the injector electromagnetic coil.When testing, unplug the two-terminal harness plug on each fuel injector, and check that the standard resistance value of the electromagnetic coil between the two terminals on the fuel injector socket should meet the requirements of the "Instructions for Use". The electromagnetic coil of the fuel injector of Santana series cars The resistance value is shown in Table 4-9. If the resistance value is infinite, it means that the electromagnetic coil is broken and the injector should be replaced.

(2) Detect the power supply voltage of the electromagnetic injector

The fuel injector power supply voltage can be detected with a digital multimeter.When testing, unplug the two-terminal plugs on each fuel injector respectively, connect the ignition switch, the engine does not start, and check the voltage between the two terminals on the plug and the engine cylinder, the high level should be about 12V (the power supply voltage of the fuel injector is the vehicle power supply voltage), and the low level is zero.If the power supply voltage is all zero, it means that the power supply circuit is blocked, and the fuel pump relay and fuel injection fuse should be repaired.

(3) Detect the control pulse of the electromagnetic injector

When detecting the fuel injection pulse voltage of the fuel injector, unplug the fuel injector harness respectively, and connect two light-emitting diodes in series between the two terminals of the plug (the two diodes are connected in parallel, and the anode of one is connected to the other. only the negative pole) and a 5100/
A coder composed of a 0.25W resistor (resistor connected in series with a diode).When starting the engine, the LEDs should blink.If the diode does not flash or glow, it means that the fuel injector power circuit, fuel pump relay or control ECU is faulty, and replace the ECU if necessary.

4. Overhaul of pulse solenoid valve idle speed control valve

The maintenance methods of various pulse solenoid valve type idle speed control valves are similar, and the Santana GLi and 2000GLi car idle speed control valves are used as examples to illustrate.

There are two terminals on the idle speed control valve of Santana GLi and 2000GLi cars, which are respectively connected to terminals 4 and 26 of the electronic control unit ECU.When the idle speed control valve fails, the idle speed control valve is in a fixed position, so that the engine idle speed rises to about 1100r/min, and the relevant information of this fault cannot be read with the VAG1551 or VAG1552 fault reader.However, you can use the "executive component diagnostic test function" of the fault reader to help diagnose whether the idle speed control valve is faulty.You can also use a multimeter to detect the resistance of the control valve coil to determine whether the solenoid valve is faulty.

(1) On-board inspection

When the engine is running at idle speed, there should be obvious vibration feeling when touching the idle speed control valve by hand.If there is no vibration or the idle speed is too high or too low, it means that the idle speed control valve is invalid and should be replaced with a new one.

(2) Detection of electromagnetic coil resistance

Turn off the ignition switch, unplug the idle speed control valve connection plug, and use a multimeter to block and detect the coil resistance between the two terminals on the socket should meet the regulations.The pulse solenoid valve type idle speed control valve has only one set of coils, and the resistance value should be about 20n.If the resistance value is infinite, it means that the electromagnetic coil is broken and should be replaced with a new one.

(3) Check the working condition of the idle speed control valve
Remove the idle speed control valve from the throttle body, and connect one terminal of it to the positive pole of the battery and the other terminal to the negative pole of the battery with a wire, the spool should move.If the spool cannot be moved, it means that the idle speed control valve is invalid and should be replaced with a new one.When a wire is disconnected, the spool should reset quickly. If the spool is stuck or cannot be reset quickly, it means that the control valve is faulty or the return spring is invalid, and a new one should be replaced.

5. Overhaul of permanent magnet rotor stepper motor idle speed control valve

The maintenance methods of the permanent magnet rotor stepper motor idle speed control valves for various types of engines are basically the same. The maintenance methods of the idle speed control valves of Toyota cars are taken as an example below.

(1) On-board inspection

When the engine is turned off, the idle speed control valve will make a "click" sound, causing the valve opening to retreat to the maximum position.If you can't hear the "click" sound when resetting, you should check the idle speed control valve.

Figure 4-39 Check the working condition of the stepper motor

(4) Detect the working voltage of the stepping motor

将怠速控制阀安装到节气门体上，插好连接器插头。当点火开关接通ON位置时，检测ECU的端子IS1、IS2、IS3、IS4与E1之间（或检测怠速控制阀连接器端子S1、S2、S3、S4与搭铁之间）应有9-14V的脉冲电压，如无电压，再检查电源电压和主继电器是否正常。

6. Overhaul of throttle control assembly J338 for Santana, Jetta and Hongqi cars

So far, most of the fuel injection systems of automobiles control the idling speed by setting a bypass air passage, and using the bypass air valve to adjust the idling speed to make the idling speed stable.Its disadvantages are complex structural design, large space occupation and high failure rate.For Santana 2000GSi, 3000, Jetta AT, GTX, and Hongqi CA7220E cars, the idle speed control method is throttle direct action, which cancels the bypass air channel leading to the throttle, and the idle speed of the engine is controlled by the throttle control component J338. Comprehensive control.

(1) Structural features of the throttle control assembly J338

节气门控制组件J338由怠速开关F60、怠速节气门位置传感器（怠速节气门电位计)G88、怠速控制电机V60和节气门位置传感器(节气门电位计)G69等组成，结构与电路连接如图4-40所示。节气门位置传感器G88和怠速节气门位置传感器G88均为线性电位器，怠速开关为触点开关。气门位置传感器G69和怠速节气门传感器G88都起着节气门位置传感器的作用。怠速控制电机V60起着控制怠速的作用，能适当开大或关小节气
(2) Detect the resistance value of the electronic winding

Pull out the connector, and use a multimeter to detect the resistance value of the stator winding on the socket, which should meet the regulations.The permanent magnet rotor stepping motor idle speed control valve has 2 or 4 sets of coils, and the resistance of each set of coils is about 30-600.If the resistance value does not meet the requirements, it should be replaced with a new one.

(3) Check the working condition of the stepping motor

Remove the idle speed control valve from the throttle, connect terminals B1 and B2 to the positive pole of the battery with wires, and then connect S1-S2-S3-S4 to the negative pole of the battery in sequence, and the valve core should gradually protrude outward, as shown in Figure 4-39 (a) shown.If you connect S4-S3-S2-S1 to the negative pole of the battery in sequence, the spool should shrink gradually, as shown in Figure 4-39(b).If the spool cannot be moved, it means that the stepping motor is invalid and should be replaced with a new one.

Therefore, the car using the throttle control assembly J338 is not equipped with an idle speed control valve.Its structure is shown in (a).

The functions of the idle switch, the idle throttle position sensor and the throttle position sensor are to provide the current position information of the throttle to the electronic control unit J220.In the idle speed range, the electronic control unit J220 adjusts the throttle opening at idle speed by controlling the idle speed motor according to these information.

① Throttle potentiometer (throttle position sensor) G69.Throttle potentiometer (throttle position sensor) G69 is directly connected to the throttle shaft and linked with the accelerator pedal operated by the driver.The sliding arm installed at one end of the throttle shaft slides on the potentiometer resistance, converts the throttle opening into an electrical signal and sends it to the electronic control unit, and provides the current throttle position signal to the electronic control unit within the engine operating speed range , as the electronic control unit also uses this signal to control the automatic transmission.If the electronic control unit does not receive the signal transmitted from the throttle potentiometer, the electronic control unit will calculate and determine a substitute value based on the engine speed signal and the air flow sensor signal.

② Idle throttle potentiometer (throttle idle position sensor) G88.The idle throttle potentiometer (throttle idle position sensor) G88 is installed in the throttle body and connected with the idle speed control motor, which can send the throttle opening and the position signal of the idle speed control electrode to the electronic control unit. When the valve potentiometer (throttle valve idle position sensor) reaches the limit of the adjustment range, the potentiometer G88 will not move any more, and the throttle valve can continue to open.When the signal of the idle throttle potentiometer (throttle idle position sensor) is interrupted, the throttle control component will use the emergency spring to enter the emergency state to work, pull the throttle to a fixed position, and increase the idle speed.

③Idle speed switch F60.The idle switch F60 is installed on the throttle shaft together with the throttle potentiometer (throttle position sensor G69), and provides idle status information to the electronic control unit.When the throttle is closed, the contact of the idle switch is closed, and the electronic control unit judges that the engine is in an idle state, so as to inject the fuel according to the idle condition; when the throttle is opened, the contact of the idle switch is disconnected, and the electronic control unit The signal controls the fuel injection quantity in the transitional condition from idle speed to light load.The idle speed switch signal can also be used as the basis for the electronic control unit to judge whether to perform automatic idle speed control and rapid deceleration fuel cutoff control.When the idle switch signal is interrupted, the electronic control unit will connect the signal of the throttle potentiometer G69 with the idle throttle potentiometer

The position meter (throttle valve idle position sensor) G88 signal is compared, and the idle position of the throttle is judged according to the mutual position of the two potentiometers.

④ Idle speed control motor V60.The idle speed control motor V60 controls the throttle valve through the gear transmission mechanism to increase or decrease the opening within the idle speed adjustment range.When the engine is idling, the idling throttle position sensor G88 converts its resistance change into an electrical signal input to the electronic control unit J220. After receiving the signal, the J220 determines the position of the throttle according to the signal voltage, and then controls the idling control motor V60. The idle speed of the engine is adjusted by micro-adjusting the opening of the throttle valve through the idle speed motor V60.

When the idle speed control motor V60 fails or the electronic control unit fails to control the idle speed motor, the emergency spring will pull the throttle to a specific emergency position, so that the idle speed will run in an emergency state, and the idle speed will increase.

(2) Overhaul of throttle control assembly J338

节气门控制组件J338连接器各端子与电控单元J220连接情况如图4-40(b)所示，连接器插头为8端子插头，端子排列位置如图4-41所示。

①Precautions for maintenance:
When overhauling the throttle control assembly, pay attention to the following points:
a. The throttle control assembly is an integral structure, and the housing is not allowed to be opened;

b. The basic setting of the idle speed parameter has been set in the electronic control unit by the manufacturer, and no manual adjustment is required;
c. After disassembling or replacing the throttle air valve control assembly, the basic setting must be performed again with the special monitor VAG1552.

d. When performing basic settings, if the following situations occur, the engine idle speed still cannot work normally.

② Overhaul of idle speed switch F60.The inspection items, inspection methods and inspection standards of the idle switch F60 are shown in Table 4-10.If the test result does not meet the maintenance standards, the throttle control assembly should be replaced.

Connect the two test leads of the digital multimeter to the wire connecting the 67 and 69 sockets of the electronic control unit, and check the resistance value of the idle speed switch.When the throttle is closed, the contact resistance of the idle contact should be less than 1.50.Then slowly open the throttle, the resistance value should be infinite.

If the resistance value does not meet the above requirements, unplug the 8-terminal plug on the throttle control assembly, and check whether there is a short circuit or open circuit fault in each wire.

(End of this chapter)