U9
Worcester Bosch Coding Plug / Configuration Fault

Boiler displays U9, often indicating a coding plug or configuration issue.

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Safety Warning

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.

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Possible Causes

Missing or incorrect coding plug, Faulty coding plug, Incorrect PCB configuration, Damaged harness to coding plug

How to Fix / Troubleshooting

Safety first: Isolate power before removing any covers.

  • Do not swap plugs yourself: The coding plug defines boiler type and settings and must match the appliance.
  • Engineer tasks: A Worcester Bosch trained engineer should verify the correct coding plug is fitted, check its connection, and reconfigure or replace the PCB if necessary.
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Repair Difficulty

Hard 4/5

Required Part

Coding Plug / Configuration Module
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