Possible reasons for the automatic transmission jerking when turned on:
1. Low transmission fluid (ATF) level
* Check the ATF level with the engine running and in park mode.
*Add ATF as needed to recommended level.
2. Dirty or old ATF
* Dirty ATF can cause clogged hydraulic passages and cause jerking.
* Replace ATF and filter according to established maintenance schedule.
3. Faulty torque converter
* The torque converter transfers power from the engine to the automatic transmission.
*A faulty torque converter can cause a jerk when shifting into gear.
4. Faulty solenoids or valves
* Solenoids and valves control the flow of ATF into the automatic transmission.
* Faulty components can cause the automatic transmission to operate unpredictably and jerk.
5. Faulty throttle position sensor (TPS)
* TPS monitors throttle position and reports information to the automatic transmission.
*A faulty TPS can cause incorrect gear adjustment and jerking.
6. Faulty input shaft speed sensor
* This sensor monitors the rotation speed of the automatic transmission input shaft.
* A faulty sensor can lead to incorrect operation of the automatic transmission and jerking.
7. Worn friction discs or clutches
* Friction discs and clutches transfer power from the transmission to the wheels.
* Worn components can slip and cause jerking.
8. Faulty Transmission Control Module (TCM)
* The TCM controls the operation of the automatic transmission.
* A faulty TCM can cause the automatic transmission to malfunction and jerk.
Solution:
* Find the cause of the twitching through diagnosis.
* Repair or replace faulty components.
* Check and replace ATF and filter if necessary.
*Calibrate TCM if necessary.