This code does not indicate necessarily a problem with a transmission control switch. It is a serial data code, and some more diagnostics will need to be done. You will need to check for codes on the ECM (Engine Control Module), the TCM (Transmission Control Module) and the EBTC (Electronic Brake Traction Control) modules to isolate this problem. Here is the description on this code.
DTC P1779, P1780, P1791, P1792, or P1795
The engine control module (ECM), transaxle control module (TCM), and the body control module (BCM) communicate with each other over the controller area network (CAN) BUS circuits 2500 and 2501. The CAN BUS is a communications protocol that is used by the TCM to communicate vital engine control inputs from a stand-alone engine controller. The diagnostic checks the information received in CAN to determine whether to pass or fail a code. Before checking the information, the TCM makes sure the CAN messages are being received by checking the BUS failure timer.
DTC P1779, P1791, P1792 or P1795 will set if the TCM did not receive a needed engine parameter over the CAN BUS from the ECM when:
• Engine speed is greater than 500 rpm for 5 seconds and not at fuel cutoff.
• System voltage between 8 and 18 volts.
• This code does not indicate a problem with the TCM. It does indicate the ECM is not sending the required information to the TCM.
• Check for and diagnose any DTCs stored in the ECM related to the ECT, pedal position or TP sensor circuits.
• Check for any DTCs stored in the EBTCM related to the torque reduction/request circuit.
Check in
THIS LINK additional information about
DTC P1780.
Hope helps.