TRANSMISSION on 2004 Cadillac DeVille

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Transmission shifting hard. Service engine light came on, and will not go off. Took to Auto Zone parts store. This is what showed on screen.TEC PREASURE CONTROL CYCLINDER P2763 PENDING
(1) Answer
Code P2763 is for a short to voltage on the Torque Converter Clutch Pulse Width Modulation Solenoid circuit. That would indicate a shorted solenoid or a wiring issue between the powertrain control module and the solenoid inside the transmission. The hard shifting is most likely due to the transmission being in a fail safe mode due to the fault code. If the fault is not intermittent the solenoid and wiring inside the transmission can be checked with and ohm meter. If the fault is intermittent the wiring should be visually inspected and if no faults are found then then replacing the solenoid as a "best guess" may be necessary.