Possible reasons:
Mechanical problems:
* Worn clutches or steel discs
* Slip torque converter
* Clogged oil filter
*Low transmission fluid level
Electrical problems:
* Faulty input shaft speed sensor
* Faulty transmission fluid pressure sensor
* Faulty shift control solenoid
Hydraulic problems:
* Faulty torque converter pump
* Clogged hydraulic lines
* Wear of hydraulic valves
Electronic problems:
*Faulty Transmission Control Module (TCM)
*Wiring problems
Other factors:
* Contaminated transmission fluid
*Low battery voltage
* Faulty brake switch
* Faulty ignition module
What to do:
1. Check the level and condition of the transmission fluid.
2. Reset transmission adaptations.
3. Carry out diagnostics using a scanner. This will help identify any recorded fault codes.
4. Check wiring and electrical connections. Make sure all wires are securely fastened and connected.
5. Inspect the mechanical components of the transmission. Please note any wear or damage.
6. Replace faulty components.
7. Update TCM software.
8. Calibrate the transmission. This may be necessary after replacing components.
Note: Automatic transmission diagnostics and repairs require specialized knowledge and equipment. It is recommended that you contact a qualified mechanic.