Most automatic transmissions have at least 3 solenoids, which are identified by the letters A, B and C. Diagnostic code P0750 OBDII refers to a fault in solenoid A.
The shift solenoid circuit allows the Power Train Control Module (PCM) to monitor the shift solenoids to control the movement of fluid between the hydraulic circuits, and also changes the transmission ratio at the appropriate time. In this way, the level of engine performance is increased to the lowest RPM.
For the transmission to change gears correctly, bands and clutches play an important role, therefore, fluid pressure in the right place is necessary. Therefore, the solenoids of the transmission open or close the valves in the body of the valve, in order to allow the fluid of the transmission to move towards the clutches and the bands. In this way, the transmission makes the changes smoothly as the engine accelerates.