LG dryers carry a feature LG calls Flow Sense. During the cycle the control watches how the exhaust behaves and, if air is leaving the drum more slowly than it should, displays d80, d90 or d95 at the end. The number expresses how severe the restriction appears; d95 is the most blocked. Clothes still dry, but they take longer, the dryer runs hotter than designed, and lint keeps collecting in a duct that is already too full. LG's guidance is to clean the exhaust system when the code appears and to have it checked if the code persists.
What Flow Sense Cannot Tell You
The dryer knows the air is restricted; it does not know where. The restriction can be the lint screen, the duct behind the dryer, the run inside the wall, or the hood outside where the flap is stuck shut with lint or blocked by a bird's nest. It also cannot distinguish a blockage from a duct that is simply too long or has too many bends for the blower to push through, which is an installation problem that presents as a permanent d80.
Start With the Screen and the Hood
Clean the lint screen and wash it in warm water with a little detergent if fabric softener has left a film that beads water; let it dry fully before refitting. Then go outside and look at the exhaust hood while the dryer runs. The flap should lift and the airflow should be obvious on your hand. A flap that barely moves confirms the problem is between the dryer and the wall.
Cleaning the Duct Safely
Before moving the dryer, unplug it. On a gas dryer, the gas shutoff valve on the supply pipe behind the dryer must be closed as well before the dryer moves, because the flexible gas connector must never be stretched or twisted, and pull the machine forward only as far as the connector allows without tension. Disconnect the duct at the dryer, then at the wall, and clean the transition duct and the wall run with a dryer-vent brush kit or a vacuum with a long attachment. Replace any plastic or thin foil duct with rigid or semi-rigid metal, keep the run short with as few bends as possible, and secure joints with foil tape rather than screws, which catch lint. Reconnect, push the dryer back without crushing the duct, open the gas valve and check for any smell before plugging in, then run a timed dry cycle and confirm the code is gone.
Why This Is Not Optional
Lint is dry, fine and flammable, and a duct packed with it sits next to a heater that runs for an hour at a time. A restricted exhaust also pushes the dryer's internal temperature up, which is exactly the condition under which lint inside the cabinet can ignite. Treat d90 and d95 as the machine asking you to remove fuel from around its heat source, not as a performance note.
When the Code Persists
If the duct is clean and short and the code returns, the blockage may be inside the dryer, in the blower housing or the internal exhaust path, or the sensor itself may be reading wrongly. Opening the cabinet to reach the blower is done with the dryer unplugged and, on gas models, the gas closed, and it is technician work. Book an LG dryer repair and say which code you see, how long the duct run is and when it was last cleaned.