Possible reasons:
Mechanical problems:
* Worn friction or clutch discs
* Torque converter malfunction
* Contamination or lack of transmission fluid
* Worn bearings or gears
*Locked shift valve or solenoid
Electrical problems:
* Malfunction in the electronic control unit (ECU) of the automatic transmission
* Damaged speed or pressure sensors
*Weak or faulty battery
Other problems:
* Alternator belt slippage
* Incorrect operation of the engine control system
Diagnostic stages:
1. Checking the level and condition of the transmission fluid: Make sure that the fluid level is correct and that the fluid does not have a burning smell or metallic particles.
2. Scan for Trouble Codes: Connect an OBD-II scanner to check for automatic transmission related codes.
3. Physical Inspection: Check for transmission fluid leaks, cable wear, or other mechanical components.
4. Test Drive: Take the vehicle for a test drive and look for any slipping, shaking, vibrations or other unusual signs.
5. Check Transmission Pressure: Measure transmission fluid pressure under various operating conditions to rule out torque converter or valve problems.
6. Clearing the DTC: If a DTC is present, refer to the vehicle’s service manual to determine the possible cause and recommended solution.
Solution:
Automatic transmission repairs can be difficult and expensive. It is recommended that you contact a qualified mechanic for proper diagnosis and repair. Common solutions may include:
* Replacement of clutches or clutch discs
* Repair or replacement of torque converter
* Changing transmission fluid and filter
* Replacement of worn bearings or gears
* Repair or replacement of electronic components (ECU, sensors, solenoids)
* Alternator belt adjustment
* Engine management system software update