Car Maintenance Basics

Chapter 12 Project Five Automobile Testing Equipment (2)
The wheel balancer is shown in Figure 5-12.After the wheels are installed with special positioning cones and fasteners, the motor can be started for balancing. When the number of revolutions is accumulated enough, the unbalanced values ​​of up and down (or left and right) can be counted. Figure 1-5 Wheel balancing machine word display, now you can stop.After the wheel stops completely, you can turn the wheel by hand, and at this time, the light-emitting diode will flash left and right (or up and down) with the rotation.If the upper row of light spots is adjusted to the midpoint, then a value balance weight can be installed on the outer edge (direction of the operator) of the upper plane of the wheel rim, and the m12 value balance weight can be installed in the same way.After the installation is completed, carry out the second test to observe whether the remaining unbalance meets the requirements of regulations.The specific operation steps are slightly different for each model, and the user should operate according to the instruction manual of the model used.

task implementation
According to the guidance of the work order, complete the operation of the common equipment for automobile maintenance. In the process of task implementation, learn the operating procedures and maintenance methods of automobile maintenance equipment, and implement in groups to complete the work within the specified time.

[-]. Tool preparation

Tip: Before implementing the homework, each group should prepare the materials and tools needed for this learning task according to the table below.

[-]. Technical standards and requirements
① All operations meet the requirements for safe operation.

② All operations are in compliance with the operating procedures of the automobile chassis testing equipment.

③ Safety accidents are not allowed during the operation.

[-]. The work to be done

1. Use of chassis dynamometer
For the operation steps, refer to the relevant knowledge content or related instructions.

2. For the operation steps of the tire dynamic balancer, refer to the equipment instruction manual.

3. The use of four-wheel aligner
Refer to the relevant knowledge content or instructions for the operation steps, and fill in the table below.

[-]. Training report

How to use and operate steps of tire changer, press machine, bench vise, connecting rod corrector, lubricating oil washer and other equipment.

Learn
[-]. Self-evaluation

1. Summary What are the main testing equipment for automobile chassis?

2. Please write down your experience of this learning task.

3. Self-evaluation of the learning environment (including dress, learning attitude, mastery of knowledge and skills, completion of work pages, etc.).

[-]. Group evaluation

Evaluation status of serial number evaluation items
Good to bad

1 team spirit
2 Whether learning is proactive
3 The situation of obeying the work arrangement

4 Use of tools and instruments
5. Tool finishing and site cleaning
[-]. Teacher Evaluation

Evaluation status of serial number evaluation items
Good to bad

1 Attendance
2 dressing situation

3 classroom order
4 Whether learning is proactive
5. Fill out the learning task book

6 Use of tools and instruments
7. Tool finishing and site cleaning
Three electrical and electronic control system testing equipment

Knowledge goal
Understand the types of testing equipment for automotive electrical and electronic control systems.

Master the basic knowledge of automotive electrical and electronic control system testing equipment.

Master the usage of testing equipment for automotive electrical and electronic control systems.

Skill Goal:
Will use automotive electrical and electronic control system testing equipment to repair the car.

Proficiency in the use of automotive multimeters, automotive oscilloscopes, decoders and other equipment.

mission details
Under the guidance of relevant knowledge, understand the basic knowledge and technical requirements of automotive electrical and electronic control system testing equipment.Under the guidance of work order tasks, it is possible to use automotive multimeters, automotive oscilloscopes, decoders and other equipment for automotive inspections.By learning and mastering the operation skills of the testing equipment of automotive electrical and electronic control systems, recording and archiving the completed work, consciously maintain safe operation and 5S work requirements.

related information
[-]. Car multimeter
The car multimeter is shown in Figure 5-13.Measuring current, voltage and resistance with a car-specific multimeter is similar to an ordinary multimeter, and the gear and range must be selected correctly before measurement.The operation methods of different multimeters may be different, and the specific operation methods refer to the accompanying instruction manual.

1. Precautions for detecting the voltage and resistance of the terminals
① Before testing, check whether the fuses and related harness plugs (connectors) of the automotive electronic control unit control system and other electrical systems are in good condition.

②When the ignition switch is in the ON position, the battery voltage should not be lower than 11V, too low battery voltage will affect the measurement results.

③ A high-impedance multimeter must be used (the impedance should be greater than 10Mn/V), and a low-impedance multimeter will damage the car's electronic control unit.It is best to use a car-specific multimeter for testing.

④ The voltage of each terminal of the electronic control unit must be measured when the electronic control unit and the harness connector (plug) are connected.And the test pen of the multimeter should be inserted from the wire side of the harness plug to measure the voltage of each terminal of the electronic control unit.

⑤ Do not directly measure the resistance of each terminal of the ECU when the wire harness and connector of the ECU are unplugged, otherwise the ECU will be damaged.

⑥If you want to unplug the connector of the electronic control unit to measure each control circuit, you should first remove the negative ground wire of the battery.Do not unplug the harness connector of the vehicle ECU when the battery is connected intact, otherwise the ECU may be damaged.

⑦When testing, first remove the wiring harness connected to the electronic control unit. When the wiring harness connector is in the connected state, according to the sequence in the testing data table, turn off the ignition switch (OFF), turn it on (ON) and turn the engine on. In the state, measure the voltage between each terminal of the electronic control unit and the ground.You can also unplug the harness connector of the electronic control unit and measure the resistance of each control circuit to determine whether the control circuit is normal.

2. Measurement of terminal voltage

① Check the battery voltage with a multimeter, it should be greater than or equal to 11V, otherwise measure after charging.

②Remove the ECU from the car, but keep the wire harness connector connected to the ECU (that is, do not unplug the wire harness).

③Place the ignition switch in the "ON" position.

④ Put the multimeter in the voltage block.

⑤Insert the test pen of the multimeter from one end of the wire of the harness plug in order to measure the voltage between the terminals of the electronic control unit.

⑥Record the voltage value between each terminal and the ground terminal, and compare it with the standard test data.If the measured voltage does not match the standard value, it means that the electronic control unit or control circuit is faulty.

3. Measurement of resistance between terminals
① Remove the ECU from the vehicle.

② Unplug the wire connector.

③Use the ohm block of the multimeter to measure the resistance value between the terminals of the wire connector (be careful not to touch the connection terminals of the electronic control unit, and insert the test pen into the wire connector from the side of the wire).

④Record the measured resistance value and compare it with the standard test data to determine whether the control circuit of the electronic control unit is normal.

⑤Even if the electronic control unit is confirmed to be faulty through the above inspection, the electronic control unit should not be discarded easily, and the method of assembly exchange should be used to confirm again whether the electronic control unit is really damaged.

[-]. Car oscilloscope
The MT2400 universal oscilloscope is shown in Figure 5-14.Its usage is as follows (take the throttle sensor as an example):
① Connect the test leads CH1 and COM according to the indicated color and turn on the power, enter the main menu, turn the wheel to select [WAVEFORMVIWER] (oscilloscope), press [Y] to confirm.

②In the oscilloscope menu, select [ground controlled] (ground control), press the [Y] key to select the appropriate amplitude and time base.

On the menu of the oscilloscope, injectors/solenoidsAgroundcontrolled (on some cars, the injector coil is computer-controlled ground, we select this function key), Apowercontrolled (on some cars, the injector coil is computer-controlled and power supply Combined, this method is rare in the market), ACpulsegeneratorsAlowfreq<120Hz (use this function key for AC pulse trigger frequency less than 120Hz), Ahighfreq100Hz-1KHz (use this function key for AC pulse trigger frequency between 100Hz and 1000Hz), digitalsignalsAlowfreq< 120Hz (use this function key for digital signal frequency less than 120Hz), Ahighfreq100Hz-1KHz (use this function key for digital signal frequency between 100Hz and 1000Hz).

③ Connect the MT2400 test instrument pen to the measured sensor signal wire and the ground wire respectively, and pull the throttle cable to fully open according to the length of the timing base to change the resistance value of the throttle sensor.

④ A smooth changing curve can be seen on the tester.Any momentary voltage dips can be seen through it.

On this interface, we can see the mode of +SLOPE or -SLOPE or RPM displayed in the lower right corner, scroll the cursor to this position, and press [Y] key to select the appropriate mode.

That is, the slope is positive, which means that the waveform starts to display when the signal voltage crosses the trigger level in the positive direction.

That is, the slope is negative, which means that the waveform starts to display when the signal voltage crosses the trigger level in the negative direction.

RPM, that is, the rotational speed signal, when the optional RPM signal sensor detects the flow of current, the waveform starts to display.At this time, what you see on the screen is a picture that scrolls on the screen with time, while the first two do not scroll with time.You can see the "+" mark on the graph, which is where the trigger level is set.The so-called trigger level setting means that under the set voltage, the meter starts to draw the waveform on the display, so the detected signal voltage must cross the set trigger level with the correct slope.If the signal waveform is not clear or scrolls on the screen, try to adjust the trigger level.To adjust the trigger level, move the cursor to the "+" mark on the screen, the trigger setting information will be displayed at the bottom of the screen, select it on the mark, press the [Y] key and the mark will start flashing.Roll the wheel to adjust the trigger level, press the [Y] key again and turn the wheel to adjust the trigger delay.Once the trigger delay is set, the waveform starts to display on the screen stably, press [N] key to exit the setting and lock the trigger setting being done.Note that the trigger level setting cannot be lower than 0V.

⑤Other potentiometers, such as accelerator position sensor, EGR valve position sensor, fuel level sensor, etc., are detected in the same way as above.

[-]. On-vehicle diagnostic system

The automotive electronic control unit (ECU) is shown in Figure 5-15.In addition to the optimal control function for each electric control system, it also has the function of fault self-diagnosis.It continuously monitors the working status of the engine's electronically controlled fuel injection system, electronic ignition advance device, engine idle speed, automatic transmission, brake anti-lock braking system, airbag system and cruise control through various sensors.

When the ECU on-board diagnostic system detects one or more fault signals and is judged to be a fault, it will automatically light up the inspection warning light on the instrument panel to remind the driver and maintenance personnel, and display the fault information as The form of fault code is stored in the memory. ECU on-vehicle diagnostic system is an important and indispensable diagnostic method for overhauling modern automobiles.

Before 1994, the form of fault codes was not uniform. According to the level of the electronic control unit installed by each car manufacturer and the needs of different uses, each car manufacturer had different forms of fault codes. Generally, this kind of electronic control unit On-board diagnostic systems are collectively referred to as the first generation of on-board diagnostic systems, namely "OBD-1". The second generation on-board diagnostic system.

[-]. Sensor simulation tester

The STS600 sensor simulation tester is shown in Figure 5-16.Its operation method is as follows:

1. connect
There are two sockets on the top of the instrument, the test line socket is on the right, and the power line socket is on the left.

When in use, insert the test line and the power cord plug into the corresponding socket respectively.The power cord has two clips, red and black, the red clip is connected to the positive pole of the power supply, and the black clip is connected to the negative pole of the power supply.The test clip also has red and black clips, the black clip is the signal common terminal (signal ground wire), the red clip is the voltage, resistance, frequency test input end and the analog voltage, analog frequency and sensor signal output end.

The measurement principle of this instrument is: for the resistance, voltage and frequency test, the test simulation tester clamp should be correctly connected to the point to be tested, and then press the corresponding test main function key.

The principle of the instrument simulation is: for the analog functions that need parameter setting, such as voltage and frequency signal simulation, you should first press the corresponding function key, and then set the parameters; press the function key again to ensure that the instrument is in the simulation state; Then connect the test clip to the analog terminal correctly.

2. Power up
Correctly connect the power cord to both ends of the car battery (12V), and the instrument will be powered on for self-test.All the characters on the display screen are displayed, and a "beep" sound is issued for about 1 second, indicating that the self-test of the meter is normal.Then the instrument enters the monitoring state, and the display screen displays the word "P", waiting for the user to select six functions.There are hints on the interface of the specific test and simulation operation steps, and you can also refer to the instruction manual of the instrument.

[-]. Fault decoder
1. Selection of test models
Kinder KT300 diagnostic instrument (Figure 5-17) is equipped with nearly 20 kinds of test connectors, which basically cover most of the common models at home and abroad.Select the vehicle type to be tested on the instrument, and select the corresponding connector according to the screen prompts. The KT300 diagnostic program uses the car model logo as a button, and the diagnosis can be performed by clicking the corresponding icon of a certain car.

2. Read and clear fault codes
Kinder KT300 diagnostic instrument can quickly read (or clear) the fault codes in the ECU memory of the system under test, helping maintenance personnel to quickly find out the cause of vehicle faults.Select in the system function selection menu.

Fault code, the system starts to detect the fault code and content confirmed by the computer. After the test of Figure 17 Kinder KT300 intelligent diagnostic instrument is completed, the test result is displayed on the screen, and all fault code information can be viewed by scrolling the screen through the scroll bar.In the process of reading the fault code, the operator can only read item by item according to the system set by the instrument, but cannot scan all the electronic control systems comprehensively.

task implementation
According to the guidance of the work order, complete the operation of the common equipment used in automobile maintenance. In the process of task implementation, learn the operating procedures and maintenance methods of automobile maintenance equipment, and implement in groups to complete the work within the specified time.

[-]. Tool preparation

Tip: Before implementing the homework, each group should prepare the materials and tools needed for this learning task according to the table below.

Data, number of names of tools Data, number of names of tools
One vehicle oscilloscope for practice

One set of engine practice bench, one set of car decoder

A set of common tools for a car multimeter

[-]. Technical standards and requirements
① All operations meet the requirements for safe operation.

②All operations conform to the operating procedures of automobile maintenance equipment.

③ Safety accidents are not allowed during the operation.

[-]. The work to be done

1. Use of multimeter
① Use a car multimeter to measure the battery voltage, please write down the measurement steps and gear selection.

②Use the car multimeter to measure the alternating current for lighting, please write down the measurement steps and gear selection.

③ Use a car multimeter to measure a resistor with an unknown resistance value, please write down the measurement steps and gear selection.

2. Use of decoder
Please refer to the relevant instructions for the operation steps.

① Please point out how many main functions does the decoder used have?
② What is the practical significance of the dynamic data stream read by the car decoder for the maintenance of the car electronic control system?
3. The use of automotive oscilloscopes
Please refer to the relevant instructions for the operation steps.Under the guidance of the teacher, please measure the waveform of a sensor and draw it.

[-]. Training report

How to use and operate the car multimeter, car oscilloscope, car decoder and other equipment.

learning assessment
[-]. Self-evaluation

1. Summarize the main equipment for the detection of automotive electrical and electronic control systems?
2. Please write down your experience of this learning task.

3. Self-evaluation of the learning environment (including dress, learning attitude, mastery of knowledge and skills, completion of work pages, etc.).

[-]. Group evaluation

Evaluation status of serial number evaluation items
Good to bad

1 team spirit
2 Whether learning is proactive
3 The situation of obeying the work arrangement

4 Use of tools and instruments
(End of this chapter)