Nikon D3400 Reference Manual - English - Page 297

Image Sensor Cleaning If you suspect that dirt or dust on the image sensor is appearing in photographs, the sensor can be cleaned manually as described below. Note, however, that the sensor is extremely delicate and easily damaged. Nikon recommends that the sensor be cleaned only by Nikon-authorized service personnel. 1 Charge the battery. A reliable power source is required when inspecting or cleaning the image sensor. Be sure the battery is fully charged before proceeding. 2 Remove the lens. Turn the camera off and remove the lens. 3 Select Lock mirror up for cleaning. Turn the camera on and highlight Lock mirror up for cleaning in the setup menu and press 2 (note that this option is not available at battery levels of H or below). 4 Press J. The message shown at right will be displayed in the monitor. Technical Notes 273