Transmission fluid (ATF) problems
*Low fluid level
* Contaminated liquid
*Wrong fluid type
* Wear of friction discs and clutches
Electrical problems
* Faulty solenoid
*Speed sensor failure
* Break in wiring
Mechanical problems
* Worn or broken gears
* Contamination in the automatic transmission
* Broken or worn timing belt/chain
Other reasons
* Faulty torque converter
* Damage to the automatic transmission housing
* Bearing wear
* Problems with the automatic transmission control module (TCM)
* Automatic transmission emergency operation mode (limp mode) due to other problems with the car (for example, engine or sensor failure)