It seems like a lot of people are having trouble with their Navien tankless water heaters failing while displaying the error code 003E 2.00. I recently saw this on my Navien NR-240A heater. According to the manual, this is caused by an ignition problem. Since there hasn't been much good information posted on YouTube as to how to fix this, I put together a video as to the steps I took to successfully bring my water heater back from the dead. This can be a DIY job, and includes cleaning the inlet air filter, replacement of the Flame Rod Assembly and, if necessary, replacing the PCB/motherboard. The only tools required are a couple of Phillips screwdrivers and no more than 90 minutes of time. The total cost in parts will be just over $200 if you order from suppliesdepot.com, and the 90 minutes of work will save you hundreds of dollars in labor.