State tankless water heater displays E11; unit may not respond to temperature adjustments.

Safety: Turn off power before handling control wiring.

• Check cable connections: Inspect the communication cable between the main control board and the remote/user interface. Ensure plugs are fully seated and not corroded.
• Inspect cable: Look for cuts, staples through the cable, or crushed sections. Replace if damaged.
• Test with known-good remote: If available, connect a known-good State remote controller. If the error clears, replace the original remote. If not, the main control board may be faulty.