Automobile Inspection Technology

Chapter 21 Detection Technology of Automotive Electronic Control System (6)
When using a multimeter to electrically block and detect whether there is an open circuit fault in the wire, the two test leads are respectively connected to the terminal 3 on the control plug and the connector jack 69 of the electronic control unit, the terminal 7 on the plug of the control component to the jack 67 of the connector of the electronic control unit, and the wire resistance Should be less than 1.5n.If the resistance value is infinite, it means that the wire is broken and should be repaired.

When detecting whether there is a short-circuit fault in the wire, the two test leads are respectively connected to terminal 3 on the plug of the control component and jack 67 of the connector of the electronic control unit or terminal 7 on the plug of the control component to jack 69 of the connector of the electronic control unit, and the resistance value should be infinite .If the resistance value is zero, it means that the wire is short-circuited and should be repaired.

In the above inspection, if the contact resistance of the idle contact is abnormal but the wire is good, it means that the idle contact is in bad contact and the throttle control assembly should be replaced.

③怠速节气门电位计G88和节气门电位计G69的检修。怠速节气门电位计G88和节气门电位计G69的检测项目、检测方法和检修标准如表4-11所示，如检测结果不符合检修标准，则应更换节气门控制组件。

Unplug the 8-terminal plug of the throttle control component, and use a multimeter to detect the idle throttle potentiometer and the power supply voltage of the throttle potentiometer between terminals 4 and 7. When the ignition switch is turned on, the power supply voltage should be at least 4.5V.

Turn off the ignition switch, unplug the J338 connection plug of the throttle control assembly and the J220 connector plug of the electric control unit, and use a multimeter to detect whether there is a short circuit or an open circuit between each terminal on the control assembly plug and each jack on the electric control unit plug. The detection parts are shown in Table 4-11.If there is a short or an open, replace the wires or harness.

④ Overhaul of idle speed control motor V60.Turn off the ignition switch, unplug the harness plug of the throttle control assembly, turn the multimeter to the electric block, connect the two ammeters to terminals 1 and 2 of the socket of the throttle control assembly, and check that the winding resistance of the idle speed control motor should be 3-200n.If the resistance value does not meet the requirements, it means that the motor is faulty and the throttle control assembly needs to be replaced.

(Section [-]) Detection of automatic transmission

The inspection of automatic transmission is divided into basic inspection, stall test, gear test, hydraulic test and road test, etc. The purpose is to discover and find out the existing problems, determine the location of the fault and take corresponding repair measures.

[-]. Basic inspection

The general faults of automatic transmissions are mostly caused by improper use, maintenance and repair. Because of the fault diagnosis of automatic transmissions, the basic inspection and adjustment of automatic transmissions should be carried out first.In this way, some faults caused by improper maintenance can be solved, and the technical status of the fault can be roughly judged, providing useful information for further fault diagnosis.

The necessary conditions for the basic inspection are that the engine of the car is working normally, the performance of the chassis is good, especially the braking performance is good.Otherwise, poor engine start, dragging of the wheel brakes, or some other problem may be misrepresented as a malfunction of the automatic transmission.

The basic inspection consists of the following series of items:

1. Automatic transmission fluid inspection

The automatic transmission fluid level check not only checks whether the automatic transmission fluid level is within the specified range, but also checks the condition of the automatic transmission fluid.

Generally, it can be checked with the oil level scale on the automatic transmission or the oil spill hole on it.The oil level gauge has double scale line type, three scale line type and four scale line type.

When checking with a double-scale oil dipstick, the oil temperature of the transmission should reach the normal operating temperature (50-80°C); then place the car on a flat ground, place the gear selection handle in each gear for a while, and then place it in the " Any one of the "P" and "N" gears; check with the oil dipstick after the engine is idling for 1 minute.At this point, the oil level should be between the two marking lines.

The oil dipstick marked with three reticles, the two areas composed of the middle scale line and the upper and lower two scale lines, some are marked with the words "COOL" and "HOT" in these two areas, and some are not.When checking with this dipstick, the lower scale area ("COOL" area) indicates the range where the oil level should be when the automatic transmission is in a cold state (below 0C); the upper scale area ("HOT') is the range where the automatic transmission oil is hot. The range where the oil level should be in the state (around 0C).

Dipsticks with 4 lines have 3 scale areas.The lowest scale area is the cold state area, the middle is the normal oil temperature area, and the uppermost is the hot state area.

If the oil level is too low, add automatic transmission oil to the filling pipe until the oil level meets the standard.Continue to run the engine, and check whether there is oil leakage in the automatic transmission oil pan, oil pipe joints, etc.If there is an oil leak, it should be repaired immediately.

The state of the automatic transmission oil is a concentrated reflection of the working state of the automatic transmission, so you should always observe the changes in the color and smell of the automatic transmission oil, and judge the quality of the automatic transmission oil and whether it can continue to be used.Table 4-12 shows the status of automatic transmission oil and common fault causes.When checking the automatic transmission oil, smell the smell of the oil from the oil dipstick, dip a little oil with your fingers and rub each other between your fingers to see if there are slag particles.

Oil temperature is another important factor affecting the service life of automatic transmission oil and automatic transmission.The main factors affecting the oil temperature are hydraulic torque converter failure, clutch and brake slipping or incomplete separation, one-way clutch slipping and oil cooler blockage, etc.Excessive oil temperature will reduce the viscosity of the oil, destroy its performance, produce grease deposits and carbon deposits, block the small measuring holes, block the control slide valve, reduce the lubrication and cooling effect, damage the seals, etc., and eventually lead to failure.

2. Engine idling inspection

An abnormal engine idle speed will affect the normal operation of the automatic transmission.If the idle speed is too low, when the gear selection handle is shifted from "N" to "R", "D", "2" or "1", the whole vehicle will vibrate, which will affect the ride comfort. Turn off the engine when changing.Conversely, if the engine idle speed is too high, there will be a shift shock, causing abnormal vehicle creep.

The engine idle speed inspection is to check whether the idle speed of the engine is within the specified range when the automatic transmission gear selection handle is placed in the "N" position.Generally, the idle speed of the car engine equipped with a microcomputer-controlled automatic transmission is 750r/min, and the idle speed should be adjusted if it is too high or too low.

During the idling inspection, the engine should be in normal working condition. After the engine temperature reaches the normal operating temperature, put the automatic transmission in neutral and start the inspection.

3. Inspection of throttle valve cable

In the automatic transmission, the throttle valve cable is connected to the throttle valve and the throttle valve on the engine. Through the displacement of the throttle valve, the throttle opening signal of the engine is converted into the oil pressure signal of the throttle valve.Throttle valve cable inspection is mainly to check whether the throttle opening, which represents the engine load, is accurately reflected on the throttle valve inside the automatic transmission.That is, the throttle valve can accurately move from the minimum opening to the maximum opening with the engine throttle under the drive of the cable.The methods to check are:
(1) Visual inspection method
Mainly observe whether the cable is damaged, whether it is fixed well, whether it is bent with the fixed part on the vehicle, whether the connection between the root of the cable and the transmission case is good, etc.

(2) Hand feeling detection method
Release the accelerator pedal to keep the throttle at the idle position, then press the cable with your fingers to check the exposed part of the throttle handle. Under normal circumstances, the cable should not be too tight or too loose.

The throttle valve cable of some automatic transmissions has a block or paint mark somewhere near the throttle end, as shown in Figure 4-42.This marking often indicates the correct position of the cable when the throttle is idling or fully open.Generally, the distance between the end of the rubber dust cover and the stop mark should be 0-1mm. If it exceeds this range, the length of the whole cable can be adjusted with the adjusting nut.

In order to better check whether the throttle cable can move flexibly in the cable sleeve and whether the throttle valve can drive the cable back to its original position, the upper end of the cable must be removed from the throttle handle, and the end of the cable must be observed. The distance between the stopper and the positioning hole on the throttle valve handle should not be too large.Then pull the cable by hand to see if it can move flexibly in the pull sleeve.

4. Inspection of gear selection mechanism

The function of the gear selection mechanism is to mechanically transmit the operator's will to the gear selection control valve (manual valve) of the transmission hydraulic control device, and transmit the execution command.If the "gear" of the gear selection control valve is bad, the components behind it will not work normally, and the transmission will not work normally.The methods for checking the gear selection mechanism are as follows:
(1) Visual inspection method
That is to observe with eyes whether the gear selection mechanism, connecting transmission rods, etc. are deformed or interfere with other parts, whether the cable is bent, damaged or folded, whether the connections are well connected and whether they are falling off, etc.

(2) Handle test method

Attach the gear selection handle to each gear according to the normal operation method, and judge whether the gear selection mechanism is working normally according to the feeling on the handle while operating.For example: whether the handle is flexible when entering each gear, whether the movement resistance of the handle is appropriate when entering the gear, whether the handle is also in the correct position after entering the gear, whether the handle is stable in the position after entering the gear and not will be easily moved.

(3) Disconnected segment inspection method
Disconnect some connecting parts of the gear selection mechanism, and then check each part in sections.Different models have different disconnection parts, but generally two-point disconnection can be used, that is, the signal transmission system of the gear selection mechanism is disconnected from two places, divided into 3 sections, and checked one by one.A breakpoint is at the connection between the rocker on the transmission shaft and the transmission cable (or pull rod). After disconnecting this point, pull the rocker on the shaft by hand to check whether each gear can be entered, and after entering Can it be locked correctly by the internal locking spring, and can it be easily pulled into other positions in this position.Through this inspection, it can be judged whether the fault occurs inside the transmission or outside the transmission.Another disconnection point is at the connection between the lever end of the gear selection handle and the cable (or pull rod). After disconnecting from here, press the normal operation, and pull the handle to check whether the gear selection work can be completed correctly.

Generally, the adjustment part of the gear selection mechanism is at the joint of the gear selection shaft rocker outside the transmission housing and the joint between the lever end of the gear selection handle and the cable (or pull rod).The main types are: lock nut type, ring groove type and lock screw type.Figure 4-43 shows the lock nut type adjustment mechanism of the gear lever system of Nissan Maxima, Duke King and other car automatic transmissions.During adjustment, the two locking nuts are moved at the same time to change the connection position between the transmission systems in the rod system, so as to realize the adjustment of the position of the rod system.

5. Inspection of neutral start switch

The purpose of the neutral start switch inspection is to check whether the engine of the car can only be started when the automatic transmission gear selection handle is in the "N" or "P" position, and whether the reversing light can only be started when the gear selection handle is in the "R" position. Only when it is turned on, so that the reversing light is on.During inspection, if it is found that the engine can start when the gear selection lever is placed in positions other than "N" and "P" (such as "D", "2", "l", etc.), adjustments should be made.

As shown in Figure 4-44, loosen the bolt of the neutral start switch, then set the gear selection handle to the "N" position, then align the neutral reference line on the neutral start switch with the groove, and keep the position still. Tighten the bolts to the specified torque.

6. Inspection of the overspeed gear control switch The purpose of the inspection is mainly to confirm whether the overspeed gear of the automatic transmission is normal.When checking, the oil temperature of the automatic transmission should be in a normal state (70-80°C), then turn off the engine, turn on the ignition switch, press the overdrive gear (0/D) control switch, and check whether the corresponding solenoid valve in the transmission is in action. If there is a "click" sound, it means that the overdrive electronic control system of the checked automatic transmission is working normally.

7. Kick-down switch check

Mainly check the sensor circuit part, check the kickdown switch installation, and open the throttle when the switch is turned on.Generally, the kickdown switch is installed on the chassis below the accelerator pedal or on the bracket at the upper end of the accelerator pedal lever.First check whether the kick-down switch is well fixed on the base plate or bracket by locking screw pair (or other methods), and whether the connection of the wire is good.Then use a multimeter to measure the resistance and voltage of the line.Under normal circumstances, the resistance value of the switch has only two states: small resistance value (-10n) and large resistance value (above 30n).The voltage value varies with different models, but it is normal when the voltage value changes significantly when the switch is turned on and off.

[-]. Test of automatic transmission

1. Road test
Road test is one of the most effective means for diagnosing and analyzing automatic transmission faults.In addition, after the automatic transmission is repaired, road tests should also be carried out to check its working performance and test the repair quality.The road test content of the automatic transmission mainly includes: checking the shifting speed, shifting quality, and checking whether the shifting actuator is slipping, etc.Before the road test, the car should be driven at a medium and low speed for 5-10 minutes to allow the engine and automatic transmission to reach the normal operating temperature.In the test, usually the 0/D switch should be placed in the ON position, and the mode selection switch should be placed in the normal mode or the economic mode.The road test method is as follows:

(1) Upshift inspection

Put the gear selector in the D position, step on the accelerator pedal, keep the throttle valve at about 50% opening, accelerate when the car starts, and check the upshift status of the automatic transmission.When the automatic transmission is upshifted, the engine speed will drop instantaneously, and at the same time, the body will have a slight jolt.Under normal circumstances, as the vehicle speed increases after the car starts, the tester should be able to feel that the automatic transmission is smoothly upgraded from the first gear to the second gear, then from the second gear to the third gear, and finally to the overdrive gear.If the automatic transmission cannot be shifted into a high gear (third gear or overdrive), it means that the control system or the shift actuator is faulty.

(2) Inspection of upshift speed

During the upshift check above, when the automatic transmission is perceived to be upshifting, note the upshift speed.Generally, the speed of a four-speed automatic transmission from the first gear to the second gear when the throttle opening is 50% is 25-35km/h.Since the upshift speed has a great relationship with the throttle opening, that is, when the throttle opening is different, the upshift speed is also different, and the transmission ratio of each gear of the automatic transmission of different car series is different, the upshift The speed is not quite the same either.Therefore, as long as the upshifting speed is basically kept within the above range, and the car accelerates well during driving without obvious shifting impact, the upshifting speed can be basically normal.If the acceleration is weak while the car is driving, and the upshift speed is obviously lower than the above range, it means that the upshift speed is too low (that is, the upshift is advanced): It means that the speed of the upshift is too high (that is, the upshift lags behind).

If the upshift speed is too low, it is generally caused by the failure of the control system; if the upshift speed is too high, it may be caused by the failure of the control system, or it may be caused by the failure of the shift actuator.

(3) Inspection of shift quality

The content of the inspection of the shift quality is mainly to check whether there is a shift shock.A normal automatic transmission can only have a less obvious shifting impact, especially the shifting impact of an electronically controlled automatic transmission should be very weak.If the shifting impact is too large, it means that the control system of the automatic transmission or the shifting actuator is faulty. The reason may be that the main oil pressure is high or the shifting actuator is slipping, and further inspection should be done.

(4) Inspection of the working condition of the lock-up clutch

Whether the lock-up clutch in the automatic transmission hydraulic transmission is working normally can also be checked by road test.In the test, let the car accelerate to overdrive, drive at a speed higher than 80km/h, and keep the throttle opening below 50%, so that the transmission enters a locked state.At this time, quickly depress the accelerator pedal so that the throttle opening exceeds 85%, and at the same time check the change of the engine speed.If the engine speed does not change much, it means that the lock-up clutch is engaged; on the contrary, if the engine speed increases a lot, it means that the lock-up clutch is not engaged. The reason is usually that the lock-up control system is faulty.

(5) Inspection of engine braking effect

When checking whether the automatic transmission has engine braking effect, the gear selector should be placed in the 2 or L position.When the car is running in second or first gear, release the accelerator pedal suddenly to check whether there is engine braking.If the vehicle speed drops immediately after the accelerator pedal is released, it means that there is an engine braking effect; otherwise, it means that the control system or the shift actuator is faulty.

(6) Inspection of kickdown function

When checking the forced downshift function of the automatic transmission, the gear selector should be placed in the D position, and the throttle opening should be kept at about 30%. Whether the transmission is forced down a gear.When kicking down, the engine speed will suddenly rise to about 4000r/min, and with the acceleration upshift, the speed will gradually decrease.If there is no kick-down after depressing the accelerator pedal, it means that the kick-down function is invalid.If the engine speed rises abnormally when downshifting, reaching 5000r/min, and there is a shifting impact when downshifting, it means that the shifting actuator is slipping, and the automatic transmission should be dismantled and repaired.

2. Manual shift test
(1. Purpose
The manual shift test is used to judge whether the fault comes from the electronic control system or the mechanical system.

(2) Test procedure
① Disconnect the shift solenoid valve connector.

②Place the gear selector in each position, and check whether the gear position is the same as that listed in Table 4-13; if there is any abnormality, it means that the fault is in the mechanical system.

③ Plug in the shift solenoid valve connector and clear the fault code.

(End of this chapter)