E19 error; controller indicates communication fault with expansion module or remote panel

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Broken bus cable, Incorrect polarity on bus terminals, Electrical interference, Failed expansion module

Safety: Isolate power before changing bus wiring.

Identify the communication bus terminals (e.g., RS485, CAN) on the main board and remote module.
Check that the bus wires are connected with correct polarity and firmly clamped.
Inspect the cable for damage along its route.
Shorten excessively long or coiled bus cables that may pick up interference, following Defro's maximum length guidelines.
Power cycle the system to re‑establish communication.

If E19 persists, the remote module or main board may require replacement.

Hard 4/5

Communication Bus Cable / Expansion Module

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