The sensing unit is mounted in the control box and must be working properly and be adjusted properly for the system to function in the automatic mode. Refer to MP45.271M for proper adjustment procedures.
A lit yellow level light indicates a side or end of the vehicle is low. When all yellow level lights are out, the vehicle should be level within the tolerances of the sensing unit, about 1-inch side to side and about 3 to 4 inches front to rear.
Use the manual buttons or move the vehicle to different locations to make sure each yellow level light will come on and can be made to go out.