98:1 Low

Viessmann 98:1 Fault Code

Also written as 981 — same fault.

The Viessmann 98:1 fault code means: your boiler is experiencing a communication error with an external remote monitoring system, meaning the central hub cannot correctly read your heating data.. It appears on 5 Viessmann models 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: Viessmann system numbers (in conjunction with monitoring of several systems via Vitocom 300)

What causes the Viessmann 98:1 fault?

This fault occurs when the boiler's main control board loses its digital connection with an external monitoring system like the Vitocom module. It is usually caused by a loose communication cable, a damaged internal coding plug, or a hardware failure within the remote monitoring interface itself.

Typical repair cost £60-120 (including labour)

DIY fix possible

Check the power supply to the Vitocom 300 communication moduleEnsure the LAN or internet cable is securely plugged into the moduleReset the communication module by turning it off and back on again

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Viessmann models that show the 98:1 fault code

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

Source

Viessmann 98:1 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.

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