P0750 = Shift solenoid A - circuit malfunction. Probable cause: wiring, shift solenoid, Engine Control Module (ECM) / Transmission Control Module (TCM).
TCM electronic control unit (TCM ECU) can be accessed using a diagnostic scantool connected to the Data Link Connector (DLC) of the car. After TCM ECU memory scaning from internal errors, (Diagnostic Trouble Codes - DTC memored), you will be able to know exactly what piece is damaged. After bad piece replacing you will be able to erase the TCM ECU memory from internal faults, and reset TCM ECU = exit transmission from 2nd gear.