E16 error and the softener reports a communication failure between display and main board.

Safety first: Disconnect power before opening the control housing. Avoid static discharge by touching a grounded metal object before handling boards.

Step-by-step:

• 1. Remove control cover: Access the display module and main PCB.
• 2. Reseat ribbon cable: Carefully unplug and replug the flat ribbon or multi-pin connector between the display and main board. Ensure it is fully seated and not reversed.
• 3. Inspect for damage: Look for bent pins, corrosion, or cracked solder joints on the connectors.
• 4. Power test: Restore power and check if E16 clears. Gently flex the cable; if the error appears intermittently, replace the cable.
• 5. Replace interface components: If reseating does not help, replace the AquaHouse user interface board first. If the problem persists, replace the main control board as well.