i1 Low

Worcester Bosch i1 Fault Code

Also written as I1 — same fault.

The Worcester Bosch i1 fault code means: this code is not an actual fault; it is simply showing your boiler's current operating status or mode of activity while it is running normally.. It appears on 1 Worcester Bosch model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Current status related boiler status code - Every operation and mode of the boiler has a related boiler status code. The boiler status code is displayed on the screen as a 3 figure number.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the i1 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch i1 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026