Possible causes of shocks when turning on the automatic transmission:
Transmission fluid problems:
*Low fluid level
* Contaminated or old fluid
Problems with torque converter:
* Worn splines
* Damaged or jammed pump blades
* Faulty damper
Problems with gear shift solenoids:
* Dirty or faulty solenoids
* Incorrect power supply to solenoids
Problems with sensors:
*Faulty throttle position sensor
* Faulty transmission speed sensor
Problems with the electronic control unit (ECU):
* Faulty ECU
* Incorrect programming
Other possible reasons:
* Worn engine or transmission mounts
* Faulty wiring
* Problems with the oil pump
* Clogged transmission fluid filter
Diagnosis and troubleshooting:
To determine the exact cause of the problem, it is recommended that you have it diagnosed by a qualified mechanic. Typically diagnosis includes:
* Checking the level and condition of the transmission fluid
* Scan fault codes
*Physical inspection of transmission and related components