Low
bF on Viessmann Vitodens 242-F FB2B

Your boiler is having trouble communicating with an optional external control system, which usually means a link device is not connected correctly or has developed a fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Incorrect LON communication module

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 242 F Fb2b installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like bF: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

bCView →bdView →

All 66 fault codes on the Vitodens 242-F FB2B

Seeing a different code? Every code this model can display, in one place.

9A9C9E9F58599294A2A4A7A8A9b0b1b4b5b7b8bAbbbCbdbEC1C2C3C4CdCFd6d7d8dAdbdCdddEdFE0E1E3E4E5E6E7E8EAEbECEdEEEFF0F1F2F3F7F8F9FAFCFdFEFF

Related guides you might find useful

Thermostat not working

Change the batteries first, even if the screen still works.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →