Hi, Shijith
Download service manual at the site, which Serg74 recommended. You can check your error codes related to the board or to the sensors. If the EST is not providing the full list of test than you have to check O2 sensor and to do the FiO2 calibration and to check the pressure sensors which are tested by ventilator during the turn-on of the ventilator. They are PT1 and PT2 pressure sensors, to check if they are OK, you need to connect a multimeter to the corresponding output of op-amplifiers type AD620 and with a tube connected to the pressure sensor and see if there are changes to the output of the corresponding op-amp, when changing your breathing. If not, I think you need to change the controller board
