Sorry it took a while ,thanks for waiting.
The manual is somewhat cryptic on this error code as it indicates a "lamp error code" , meaning the LED backlighting.
This in turn points to a defective power/inverter board part # RUNTKA684WJQZ , but then again the error code is not always an exact diagnostic and often just points in the direction where you would start troubleshooting.
You could try to replace that board yourself and there is a very good chance that it would clear the problem but without being there with tools and meters myself, it would be difficult to confirm that.
Not sure if you had an idea about looking into repairing this yourself but if you do then you could get that board at the link below;
If not then I would recommend a sharp ASC (authorized service center) , you can find the nearest one at the link below;
Just enter your model and zip code.
Wish i had better news and an easier solution for you today but i hope this help and I will be in standby if you have any questions.
Thank you and please take the time to rate my answer if that answers your question and you can still reach me here at anytime after this chat is closed if you have other questions.
Please note that from where i`m sitting there is just so much that i can do and if you are going to rate my answer below O.K service then please do not rate at all , just let me know.