Abnormal Pcb Navien. That has electronic memory component 'chips' on it. Navien error code e004 is an indication that the unit is detecting a false flame.
It is a sort of computer that receives data from the sensors in the. On your navien tankless water heater, the fault code e438 indicates the recirculation pump is operating abnormally. Navien flow sensor problems are some of the more common issues, and they are usually caused by a clogged or rusted sensor.