Automobile Inspection Technology

Chapter 24 Detection Technology of Automotive Electronic Control System (9)
①Remove the tilt and telescopic ECU with wire connector, connect the positive pole of the voltmeter to the connector terminal UWSW, and the negative pole to ground.When inserting and pulling out the key, the readings on the meter should be 0V and battery voltage respectively.If it meets the requirements, go to the next circuit inspection in Table 4-18 of fault symptoms; if it does not meet the requirements, go to step ②.

② Unplug the wire connector of the unlocked alarm switch, and use an ohmmeter to detect the resistance value between the switch terminals 9 and 10.When inserting and pulling out the key, the meter should read 0n and infinite ohms respectively.If it does not meet the requirements, replace the unlocked alarm switch; if it meets the requirements, go to step ③.

③ Check the wiring and connector between the tilt and telescopic ECU and the unlocked alarm switch, if it is defective, repair or replace the wiring or connector; if it is good, check or replace the tilt and telescopic ECU.

[-]. Electronic control system detection

The structural diagram of the power steering electronic control system is shown in Figure 4-69, and the circuit diagram of the power steering electronic control system is shown in Figure 4-70.

1 - liquid storage tank; - impeller pump; - vehicle speed sensor; - power steering ECU; - electromagnetic regulating valve; - flow distribution valve;, 13 - rack;

8-小齿轮；9一液力反应腔；10-活塞；11一动力转向活塞；2-动力转向油缸；14一控制阀轴；15-扭力杆；16-旋转滑阀
The system detection and troubleshooting procedures of the power steering electronic control system are as follows:

①Turn on the ignition switch and check whether the ECU-IG fuse is normal.If it is not normal, replace the fuse and check again; if it is normal, it can be determined that the fuse is faulty; if it is still not normal, check whether there is a short circuit between the fuse and the ECU terminal + B; if normal, Enter step ②.

② Unplug the ECU connector and check whether there is battery voltage between the ECU connector terminal +B and the body ground.If there is no battery voltage, check whether there is an open circuit in the wiring between the fuse and the ECU connector terminal +B; if so, go to step ③.

③Use an ohmmeter to check whether there is continuity between the ECU connector terminal GND and the vehicle body ground.If there is no conduction, check the wiring between the ECU connector terminal GND and the body ground for disconnection or poor grounding of the body; if conduction, proceed to step
Step ④.

④ Check the signal voltage of the speed sensor.Use a jack to jack up the rear wheel on one side, connect the voltmeter to the connector terminals SPD and GND of the ECU, turn to the rear wheel: for UCF10 series vehicles, the reading of the meter should be 0V->5V-0V; for UCF20 series For vehicles, the meter should read 0V-infinity-0V.

If it is not correct, check that there is an open circuit or short circuit between the ECU connector terminal SPD and the speed sensor, or the speed sensor is faulty; if it is correct, go to step ⑤.

⑤Use an ohmmeter to check whether there is continuity between the ECU connector terminal S0L+ or SOL- and GND.If conduction, check the wiring short circuit between the ECU connector terminals S0L+ and SOL- or the solenoid valve is faulty; if it is not conduction, go to step ⑥.

⑥ Check the resistance value between the terminals S0L+ and SOL- of the ECU connector with an ohmmeter.The normal resistance value is 6.0-11.00.If the resistance value is incorrect, check that the wiring between the ECU connector terminals S0L+ and SOL- is open or the solenoid valve is faulty; if the resistance value is correct, check or replace the power steering ECU.

(Section [-]) Detection of brake anti-lock braking system

[-]. Read and clear fault information
Modern automotive electronically controlled anti-lock braking systems all have a fault self-diagnosis function. When the ECU of the ABS system detects system fault information, it immediately lights up the ABS warning light on the instrument panel to inform the driver that the ABS system has a fault, and at the same time Fault information is stored in the memory in the form of fault codes.When diagnosing the fault of the ABS system, the fault code can be read and cleared according to the set procedure and method.Retrieving, reading and clearing the diagnostic fault codes becomes the key to the detection work. The so-called "reading" refers to reading the specific meaning of the fault codes in order to make an exact diagnosis.The following describes the reading and clearing methods of common vehicle fault codes.

1. Retrieving and clearing the fault codes of the ABS system of Toyota vehicles

(1) Reading of fault codes
① Separate the maintenance connector joints or pull out the short-circuit pin between WA and WB, as shown in Figure 4-71.

②Turn on the ignition switch.

③ Connect the TC and E1 terminals of the fault diagnosis seat in the engine room or the TDCL connector in the cab with a jumper wire, and the ABS warning light on the instrument panel will flash a fault code.Refer to the following table for the fault code code and the fault content.

2. Reading and clearing the fault codes of the ABS system of Audi cars

The ABS diagnostic connector is installed in front of the transmission lever, and the ABS fault can be read through the LED test light and the jumper wire.

Fault codes, quickly find the cause and location of the fault.

(1) Read the fault code

When the car is running, if the ABS breaks down, the ABS warning light on the dashboard of the cab will be on, prompting the driver that the car has broken down.

①断开点火开关，将LED测试灯连接在2号和10号诊断接头位置，跨接2号和9号端子，如图4-72所示。

②Turn on the ignition switch, and after about 4 seconds, remove the No. 2 and No. 9 jumper wires.

③If there is no fault in the system, the code 4444 will indicate that the system is normal.

④ If the system fails, read the fault code in the form of the flashing alarm light, as shown in Figure 4-73.Ground the jumper once (more than 5s), and a group of fault codes will flash. Each group of fault codes consists of 4 digits. Each number is represented by the number of times the alarm light flashes. The fault codes are displayed in ascending order.

⑤When the self-diagnosis is over, it will flash four times for 4s continuously, representing the end code of 2.5.

(2) Clear fault codes

After overhaul, connect the LED test light to the No. 2 and No. 10 diagnostic connectors, jumper the No. 2 and No. 9 terminals and turn on the ignition switch. After at least 5 seconds, remove the No. 2 and No. 9 jumper wires.If the LED test light and the alarm light on the instrument panel are still on, jumper the No. 2 and No. 9 terminals for at least 5 seconds, remove the jumper wire, and the LED test light goes out, indicating that the fault code has been cleared.

[-]. Fault codes and their meanings

The fault self-diagnosis function of the ABS system may vary slightly depending on the model, and should be carried out according to the maintenance manual of the model.According to the fault codes read out, the location and cause of the fault can be judged in time. In addition to the fault codes and their meanings of the ABS system of Toyota and Audi cars mentioned above, the fault codes of ABS systems of several models are introduced below. and its meaning.

1. The fault codes and meanings of the ABS system of Volkswagen cars

[-]. ABS system circuit detection

The detection of the ABS system circuit is mainly to detect the voltage/resistance of the vehicle speed sensor, the resistance/action response of the ABS solenoid valve, the switch circuit, the voltage/resistance of the relay, and the voltage/resistance of the hydraulic pump relay.Here we take the ABS system circuit of the Audi car as an example to explain.

1. Audi car ABS circuit detection

When testing the vehicle speed sensor, turn off the ignition switch and turn the wheels at a speed of 60r/min. Measure the output voltage of the vehicle speed sensor with an AC voltmeter and meet the requirements in Table 4-25. Measure the resistance of the vehicle speed sensor with an ohmmeter and meet the requirements in Table 4-26. Require.

(Section [-]) Testing and Training of Automotive Electronic Control System

[Training project [-]] Fault detection and diagnosis of engine electronic control system
1. Purpose of training
① Familiar with the structure and working principle of each component in the electronic control system.

②Learn the basic usage of the decoder.

③ Able to independently draw the circuit diagram of the wiring connection between each component in the electronic control system and the electronic control unit.

④ Familiar with the meaning of each sensor, electronic control unit (ECU) and actuator connector terminals.

⑤ Familiar with the maintenance methods of each component of the electronic control system.

⑥Be proficient in the detection and diagnosis methods and operation skills of common faults in electronic control systems.

2. Training content
① Analyze the structure and working principle of each component of the engine electronic control system (sensors, actuators, ECU) one by one, and the impact on the normal working conditions of the engine.

② Use a multimeter to measure the circuit connection between the sensors and actuators of the electronic control system and the central control computer (ECU)

the way.

③Measure the meaning of each connection terminal of each component of the engine electronic control system (sensors, actuators, ECU) one by one, and measure the relevant voltage values ​​under different engine working conditions.

④ Analyze the cause of failure of the relevant electronic control system that the engine cannot start normally or cannot work normally after starting.

⑤ Set up the faults of the electronic control system, think independently and eliminate them.

3. Training equipment and instruments

① Engine electronic control training platform.

② Jumper wires, LED test lights, multimeters, professional detectors (decoders), oscilloscopes, etc.

4. Training steps
① Check and analyze all sensors and actuators of the engine electronic control system.

②Use a multimeter to detect the connection mode between the sensors and actuators of the engine electronic control system and the ECU terminals, and measure the voltage of some terminals or the resistance value between terminals.

③Analyze the reasons why the engine cannot start or run abnormally.

④ Check the sensors and actuators of the engine electronic control system (for detailed testing items, steps and methods, please refer to Chapter 4 (Section [-]) of the textbook).

⑤ Analyze the faults and maintenance methods of the engine oil supply system.

⑥ Analyze the faults and maintenance methods of the engine ignition system.

⑦ Analyze the troubleshooting ideas of the engine electronic control system.

⑧Set the faults that the engine cannot start or is abnormal after starting, troubleshoot on site and write a detailed fault analysis report.

[Training project [-]] Fault detection and diagnosis of automatic transmission electronic control system
1. Purpose of training
① Familiar with the structure and working principle of each component in the electronic control system.

②Learn the basic usage of the decoder.

③ Able to independently draw the circuit diagram of the wiring connection between each component in the electronic control system and the electronic control unit.

④ Familiar with the meaning of each sensor, electronic control unit (ECU) and actuator connector terminals.

⑤ Familiar with the maintenance methods of each component of the electronic control system.

⑥Be proficient in the detection and diagnosis methods and operation skills of common faults in electronic control systems.

2. Training content
① Analyze the structure and working principle of each component (sensors, actuators, ECU) of the automatic transmission electronic control system one by one, and the impact on the normal working condition of the engine.

②Use a multimeter to measure the circuit connections between the sensors and actuators of the electronic control system and the central control computer (ECU).

③ Measure the meaning of each connection terminal of each component (sensor, actuator, ECU) of the automatic transmission electronic control system one by one, and measure the relevant voltage values ​​under different transmission conditions.

④ Analyze the reasons why the automatic transmission cannot work normally and the normal gear changes or intelligent control.

⑤ Set up the faults of the electronic control system, think independently and eliminate them.

3. Training equipment and instruments

① Automatic transmission electronic control training platform.

② Jumper wires, LED test lights, multimeters, professional detectors (decoders), oscilloscopes, etc.

4. Training steps
① Analyze the sensors and actuators of the automatic transmission electronic control system.

② Use a multimeter to detect the connection mode between the sensors and actuators of the automatic transmission electronic control system and the ECU terminals, and measure the voltage of some terminals or the resistance value between terminals.

③ Analyze the phenomena that the automatic transmission cannot work normally.

④ Analyze the reasons why the automatic transmission cannot work normally.

⑤ Analyze the troubleshooting ideas of the automatic transmission electronic control system.

⑥Set the failure of the automatic transmission to work or not work normally, troubleshoot on-site and write a detailed failure analysis report.

【Training project [-]】ABS electronic control system fault detection and diagnosis
1. Purpose of training
① Familiar with the structure and working principle of each component in the electronic control system.

②Learn the basic usage of the decoder.

③ Able to independently draw the circuit diagram of the wiring connection between each component in the electronic control system and the electronic control unit.

④ Familiar with the meaning of each sensor, electronic control unit (ECU) and actuator connector terminals.

⑤ Familiar with the maintenance methods of each component of the electronic control system.

⑥Be proficient in the detection and diagnosis methods and operation skills of common faults in electronic control systems.

2. Training content
① Analyze the structure and working principle of each component of the ABS electronic control system (sensors, actuators, ECU) one by one, and the impact on the normal working condition of the engine.

②Use a multimeter to measure the circuit connections between the sensors and actuators of the electronic control system and the central control computer (ECU).

③ Measure the meaning of each connection terminal of each component (sensor, actuator, ECU) of the automatic transmission electronic control system one by one, and measure the relevant voltage values ​​under different transmission conditions.

④ Analyze the reasons why the ABS system does not work normally, that is, the brake control is implemented.

⑤ Set up the faults of the electronic control system, think independently and eliminate them.

3. Training equipment and instruments

① Anti-lock braking (ABS) electric control training platform.

② Jumper wires, LED test lights, multimeters, professional detectors (decoders), oscilloscopes, etc.

4. Training steps
① Analyze the sensors and actuators of the ABS electronic control system.

②Analyze the connections between the sensors and actuators of the ABS electronic control system and the ECU terminals, as well as the voltage and resistance values ​​of certain terminals.

③ Check the ABS circuit (for detailed testing items, steps and methods, please refer to Chapter 4 (Section [-]) of the textbook).

④ Analyze the reasons why the ABS cannot work normally.

⑤ Analyze the troubleshooting ideas of the ABS electronic control system.

⑥Set the failure of ABS not working, troubleshoot on-site and write a detailed failure analysis report.

thinking and practice
1. Briefly describe the functions of the vehicle-specific detector (decoder).

2. Compare and analyze the difference between using off-car and on-car injector cleaners to clean the injectors.

3. Briefly describe the functions of the OBDn system.

4. How to detect the technical condition of the air flow meter?
5. Briefly describe the detection method of the fuel pump control circuit of the electronically controlled gasoline engine.

6. What are the main testing items of automatic transmission?

7. How to judge the condition of automatic transmission through the detection of automatic transmission oil?
8. What are the main items of the automatic transmission gear test and how to proceed?

9. What are the methods to read the fault codes of the anti-lock braking system?

10. Briefly describe the contents of the circuit detection of the brake anti-lock braking system.

11. Briefly describe the contents of electric steering system (PSS) circuit detection.

(End of this chapter)