- Reduced engine recoil efficiency;
- Violation of regulations;
- Hydraulics malfunction;
- Mechanical damage;
- Failures of the onboard processor / its signal circuit.
Failure diagnosis should always start with the simplest checks: check the level and condition of the ATF (see chapter Vehicle settings and routine maintenance), check the adjustment of the gearshift and throttle actuators. Next, test drive the vehicle to determine the effectiveness of the corrections made. If the problem cannot be fixed, you should drive the car to a service station for more detailed diagnostics using special equipment. A description of some of the symptoms of AT dysfunction is given in the Section, dedicated to the diagnosis of failures of components and systems of the car at the beginning of this guide.
Primary Checks
1. During a short drive, warm up the transmission to normal operating temperature.
2. Check the ATF level (see chapter Vehicle settings and routine maintenance):
- a. If the liquid is clearly not enough, make the appropriate adjustment by adding the required amount of fresh ATF. Verify that the dipstick adjustment is correct, then check the transmission for signs of external leaks (see below);
- b. If the level is excessively high, drain excess ATF, then check it for signs of coolant presence, indicating a leak in the internal bulkheads of the radiator separating its heat exchanger from the side tanks with ATF (see chapter Engine cooling, interior heating and air conditioning systems);
- c. If the ATF is foamy, empty the transmission and refill it with fresh fluid - check the drained ATF for signs of coolant presence.
3. Check engine idle speed setting (see chapter Vehicle settings and routine maintenance). If necessary, drive the car to a workshop to make the appropriate adjustments.
Note. If the engine is out of order, you should not proceed with the initial checks of the transmission until the appropriate corrections have been made.
4. Make sure that the gearshift linkage is properly adjusted and runs smoothly (see Section Shift rod adjustment).
Diagnosis of ATF leaks
General information
Most leaks are easily identified by visual inspection. Repair usually consists of replacing the corresponding defective oil seal or gasket. If the external inspection fails to identify the source of the leak, proceed as described below.
1. First of all, it is necessary to exclude the possibility of error in determining the nature of the leak. ATF should not be confused with engine oil or brake fluid (transmission fluid is usually dark red in color).
2. Run a short test to find the source of the leak (several kilometers) ride, then park the car over a blank sheet of cardboard. After a couple of minutes, the source of the leak can be identified by traces of liquid dripping onto the cardboard.
3. Carefully inspect the suspected area and the surrounding surface, paying special attention to the joints of the mating surfaces. In order to expand the viewing angle, use a pocket mirror.
4. If you still cannot find the source of the leak, carefully wipe the surface of the suspected area with a rag soaked in solvent, then dry it.
5. Drive another short drive, this time changing speed frequently, then re-examine the cleaned suspect area.
6. After identifying the source of the leak, it is necessary to determine and eliminate the cause of its development, and only then proceed to perform the necessary restoration work. Replacing a damaged gasket will not lead to the desired result if the defect in the mating surface that led to the failure of the seal is not corrected. So, the deformed flange must be straightened.
The following subsections list the most common causes of ATF leaks and the conditions that must be met to prevent recurrence.
Note. Some of the listed requirements cannot be met without the use of special equipment. In this case, the car should be driven to a service station.
Leakage through gasket surfaces
Periodically inspect the transmission oil pan. Check that the fixing bolts are in place and securely tightened, make sure that there are no signs of mechanical damage on the cover (deformation of the sump can lead to failure of the valve assembly located inside the transmission).
Possible reasons for the development of leaks through the sump include excessively tight tightening of the mounting bolts, violation of the patency of the ventilation line, mechanical damage to the sealing surface of the transmission case, destruction of the gasket, as well as the occurrence of cracks or porosity of the walls of the case. If the gasket of the pan or transmission case is formed by a sealant pad, the possibility of an incorrect choice of the type of the latter cannot be ruled out. Pan gasket leaks can also be caused by overfilling the crankcase with transmission fluid or by increasing ATF pressure.
Leaks through glands and cuffs
The most typical causes of transmission oil seal failure include excessively high ATF level/pressure, vent pipe obstruction, mechanical damage to the walls of the seat, damage to the oil seal itself, or improper installation of the latter. It is also possible that the trunnion of the shaft threaded into the stuffing box is damaged, or the latter has excessive play as a result of bearing wear.
Check the condition and correct fit of the sealing collar of the dipstick guide tube. Periodically inspect the surface around the speedometer/speedometer drive gear for signs of leaks (VSS). If necessary, replace the sealing ring.
Leaks through defects in the walls of the transmission case
The reason for the development of ATF leaks may be the formation of cracks or pores in the body of the transmission housing, consult a car service specialist.
Check the tightness of the union connections of the ATF cooler hoses.
Note. Leaks through the breather and filler neck
Breather or filler leaks can be caused by an overfilled transmission, coolant in the ATF, a blocked breather/vent or return drains.
Diagnostics of other AT failures
Check of serviceability of functioning of electronic subsystems AT
The composition of the electronic part of the control system for the functioning of the AT includes a self-diagnosis system, which, by means of a control lamp for switching off the overdrive (O/D OFF) alerts the driver to transmission problems. Using the same control lamp, you can determine the code of the malfunction stored in the memory of the device.
Note. Warning and reading of fault codes become possible only when the OD mode is on (the switch is in the ON position), as otherwise the control lamp will burn constantly in its normal mode.
In the event of a malfunction of the speed sensors (VSS #1 or #2) or one of the solenoid valves (No. 1, 2 or 4) the control lamp will flash, warning the driver of a malfunction. In case of failure of the solenoid valve No. 3 (torque converter clutch control valve) there will be no error warning.
The fault code that has occurred in the transmission can be determined using the same warning lamp: for this, it is necessary to bridge the conclusions «TE1» and «E1» diagnostic connector (refer to accompanying illustration).
Check of serviceability of functioning of mechanical subsystems AT
Fully braked test (stall test)
The performance of the transmission and engine is made by measuring the crankshaft speed in the positions «R» and «D» AT with a fully braked car.
Attention! ATF must be warmed up to normal operating temperature (50–80 deg.). The duration of each check should not exceed 5 seconds.
The check should be carried out by two people: one must observe the wheels of the car, the second performs the necessary manipulations in the car.
1. Brake the front and rear wheels of the car.
2. Connect a tachometer to the engine.
3. Fully apply the parking brake.
4. Depress the foot brake pedal as far as it will go.
5. Move the transfer case control lever to the position «H».
6. Start the engine. Move the AT selector lever to position «D», fully depress the gas pedal and quickly read the tachometer readings.
Attention! If, during the test, the rear wheels of the vehicle begin to rotate before the engine speed reaches the required value, release the gas pedal and stop the test.
7. Carry out a similar check with the transmission in position «R».
If the engine speed in both cases is the same and lower than required, therefore, the engine does not develop full power, or the AT torque converter freewheel is faulty.
If the engine speed is higher than required in the transmission position «D», this may indicate an excessive decrease in pressure in the main line, slipping in the freewheel No. 2, a malfunction of the freewheel of the increasing planetary gear set, or slipping in the direct clutch of the transfer case.
Exceeding the engine speed in position «R» transmission indicates a pressure drop in the main line, slip in the direct clutch, slip in the brake of the first and reverse gears, malfunction of the freewheel of the boosting planetary gear set, or slip in the direct clutch of the transfer case.
If the engine speed is too high in both transmission positions, then either the pressure in the main line has dropped excessively, or the ATF level does not correspond to the required value, or the freewheel clutch of the boost planetary gear set is malfunctioning, or there is a slip in the transfer case direct clutch.
Checking the switching delay time
If the selector lever is moved to one of the forward ranges while the engine is idling, some time must elapse before the start of movement. By the duration of this delay, one can judge the proper functioning of the interlocking clutches of the increasing planetary gear set, forward gear, direct gear and the first and reverse gear brakes.
Attention! The check should be made with the engine warmed up to normal operating temperature. The final result should be obtained by averaging the results of three tests, between each of which there should be at least one minute. Below is a detailed description of the progress of this check.
1. Fully apply the parking brake. Move the transfer case control lever to position «H».
2. Start the engine and check its idle speed (see Chapter Vehicle settings and routine maintenance), – make appropriate adjustments if necessary.
3. Move the selector lever from the position «N» into position «D» and use a stopwatch to measure the delay time - the average value of three consecutive measurements should not exceed 1.2 seconds.
4. Proceeding in a similar manner, determine the delay time for engaging the reverse gear, which should not exceed 1.5 seconds.
Excessive turn-on delay may be due to too low main line pressure, malfunction of the forward clutch, planetary boost clutch, or first and reverse brakes.
Hydraulic test
The check is carried out by two people.
The test is carried out when warmed up to normal operating temperature (50–80 deg.) ATF.
1. Unscrew the plug from the transmission housing and screw in its place the nozzle of a special pressure gauge.
2. Apply the parking brake.
3. Start the engine and check that the idle speed is set correctly (see chapter Vehicle settings and routine maintenance), - make appropriate adjustments if necessary.
4. Depress the foot brake pedal and move the selector lever to the position «D».
5. Read the pressure gauge reading with the engine idling.
6. Press the gas pedal all the way down and read a new meter reading at maximum engine speed.
Note. If the rear wheels start spinning before the RPM reaches maximum, release the throttle immediately and abort the test.
7. Proceed in a similar manner to take measurements in reverse mode.
8. Compare the measurement results with the pressure map in the main line (pressure map available from Toyota dealers).
9. If the pressure in both ranges is too high, you should adjust the accelerator cable, check the condition of the throttle and / or pressure regulator.
The reasons for the underestimated results, in addition to those listed above, may also be a malfunction of the oil pump, and failure of the blocking clutch of the increasing planetary gear set, the direct clutch of the planetary gear set of the transfer case (H), transfer box forward clutch (H, L), or the transfer case downshift brake (L).
If the pressure is underestimated only in the mode «D», therefore, there is a leakage of working fluid in the control circuit in the appropriate range, or the forward clutch is faulty.
The reason for the underpressure in the mode «R» may be a leak of the working fluid in the appropriate range, or a malfunction of the first and reverse brakes.
Sea trials
Attention! The tests shall be carried out at normal operating temperature (50–80°C) ATF.
Range check «D» in normal and sport modes of operation
1. Move the AT selector lever to position «D», depress the accelerator pedal as far as it will go and hold it in this position. Check shift points 1-2, 2-3 and 3-4, - compare test results with standard values.
2. Check is made for normal and sports modes of functioning of АТ.
3. The absence of switching 1-2 indicates the failure of the electromagnetic valve No. 2, or the sticking of the valve 1-2.
4. Solenoid valve No. 1 is responsible for the lack of switching 2-3, and the possibility of sticking the switching valve 2-3 is also possible.
5. If there is no switching 3-4, check the condition of valve 3-4.
6. The reason for the failure of the shift points may be a malfunction of the throttle and shift valves 1-2/2-3/3-4.
7. Lack of lockup of the torque converter is due to the failure of the solenoid valve No. 3, or sticking of the lock-on valve.
8. Evaluate the smoothness of the gear shift. The cause of the shocks may be excessively high pressure in the main line, a malfunction of the hydraulic accumulator, or a control ball valve.
9. When driving with a locked torque converter or in 4th gear, evaluate the intensity of vibrations and background noise.
Note. The reason for the occurrence of vibrations and noises can also be a violation of the balance of cardan shafts.
10. Accelerate the car to 4th gear and, while braking, determine the shift points 4-3, 3-2 and 2-1. Compare test results with standard values.
11. Estimate smoothness of switching.
12. Check the quality of the torque converter blocking, with a uniform movement in 4th gear, blocking should occur at a speed of approximately 75 km / h. Slightly press the gas pedal - the engine speed should not change noticeably, otherwise the torque converter lock is broken.
Range check «2»
1. Move the AT selector lever to position «2», depress the accelerator pedal as far as it will go and hold it in this position.
2. Determine the switching point 1-2, compare the test result with the standard requirements.
Note. In this mode, switching 2-3, 3-4 and blocking the torque converter are prohibited; when driving at a speed of 100 km / h and above, engine braking is prohibited.
3. While moving in 2nd gear, release the gas pedal and evaluate the effectiveness of engine braking of the car. If there is no braking, then the brake for providing this mode is faulty.
Range check «L»
When the mode is turned on «L» any overshifting is prohibited - the car must move all the time in first gear.
1. Release the gas pedal and evaluate the intensity of engine braking. If there is no braking, then the brake for engaging the first and reverse gears is faulty.
2. Estimate the level of noise and vibrations during engine braking.
Range check «R»
Move the AT selector lever to position «R» and start moving with the gas pedal pressed to the stop, there should be no slipping of the friction controls.
Range check «R»
Park the vehicle on a slope of at least 5°and move the selector lever to the «R», do not apply the parking brake - the vehicle must remain stationary.