Zanussi Ultra System Fault codes & diagnostics

3 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

System Natural Gas 2005-2017 Discontinued
GC Numbers 41-002-0141-002-0241-002-0341-002-04
Download the Zanussi Ultra System manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Zanussi Ultra System faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

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C0

Your boiler has encountered a temporary system error and requires a simple manual reset to try and resume normal operation.

Medium DIY-safe £0-120

What to check first

  1. Locate the 'Reset' button on the boiler control panel.
  2. Press and hold the button for 3 to 5 seconds.
  3. Wait a few minutes to see if the boiler fires up and the error code clears.

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Control module

Related codes

Full explanation for C0
C2

Your boiler has lost communication with its internal computer chip, meaning the main control board no longer recognizes the specific model it is supposed to be operating.

High Engineer only £100-£350

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for C2
L1

Your boiler has shut down because the water inside it has become too hot, usually due to a lack of circulation or a blockage in the system.

High DIY-safe £100-350

What to check first

  1. Check that your radiator valves are fully open.
  2. Ensure the boiler pressure is between 1 and 1.5 bar on the gauge.
  3. Reset the boiler by turning the control knob to 'Reset' and then back to 'On'.

Parts commonly replaced

  • Pump
  • Flow Thermistor
  • Heat Exchanger

Related codes

Full explanation for L1
Status & diagnostic codes

5 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

oF Diagnostic Your boiler is in a standby or programming mode and thinks it has been told to stay switched off. P1 Diagnostic Your boiler is displaying a service setting notification rather than a breakdown, indicating the internal pump is being told to run at its maximum speed. SE Diagnostic Your boiler is simply reminding you that its annual service is due soon; it is a notification rather than a breakdown. SL Diagnostic Your boiler is currently running a service test at its lowest power setting and this is a status indicator rather than a functional error. uP Diagnostic Your boiler is currently stuck in its startup or programming sequence and is not yet ready to provide heat or hot water.