Low transmission fluid level
Dirty transmission fluid
Faulty shifting solenoid valve
Shifting solenoid valve harness is open or shorted
Shifting solenoid valve circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
Transmission may not shift to the next gear
This P0783 code indicates that the 3-4 shift valve in the valve body is locked in the direction of the spring compression. The Transmission Control Module (TCM) controls the gearshifts by turning the shift solenoid valves ON/OFF and switching oil pressure to the valves in the valve body. The TCM calculates the actual transmission gear by comparing the signals from the input speed sensor and the output speed sensor. The P0783 code is detected when the actual gear position and the commanded gear position are different.