Possible reasons:
Mechanical faults:
* Wear of clutches or steel discs in the gearbox
* Torque converter malfunction
*Damage to planetary gear
*Low transmission fluid (ATF) level
Electrical/electronic faults:
* Malfunction of solenoids
*Transmission ECU problems
* Poor contacts in electrical wiring
* Faulty speed or throttle position sensor
Troubleshooting:
1. Check ATF level: Check the fluid level with the engine warm and the transmission running. If the level is low, add fluid recommended by the manufacturer.
2. Scan for trouble codes: Use an OBD-II scanner to check for transmission-related trouble codes. The codes will help identify the faulty component.
3. Check the solenoids: Use an oscilloscope to check the functionality of the solenoids. Faulty solenoids can cause the transmission to not operate properly.
4. Inspect the torque converter: Remove the torque converter and inspect the internal components for wear or damage.
5. Inspect the planetary gear: Remove and disassemble the gearbox to inspect the planetary gear. Look for worn or damaged gears or bearings.
6. Check Wiring: Inspect the wiring to the transmission and ECU for damage or poor connections.
Recommendations:
* Change ATF and filter regularly according to manufacturer’s recommendations.
* Avoid sudden acceleration and deceleration.
* If symptoms of malfunction occur, contact a qualified mechanic immediately.
*Diagnosing and repairing automatic transmissions can be challenging, so it is recommended that you contact an experienced transmission technician.