F.93 on a Viessmann One Base: M2IO electronics module communication error
Short answer
On a Viessmann heat pump, F.93 means: M2IO electronics module communication error. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: M2IO electronics module communication error.
Part involved: M2IO electronics module communication error.
When it shows: System characteristics: Function of connected components in emergency mode.
Likely causes:
- M2IO electronics module communication error.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Not stated per code in Viessmann document 6171807 GB 10/2021.
Manual reset: User may acknowledge via HMI after noting the code (6249162 p.57); the message returns if the cause persists.
What you can check
- On the HMI, tap the message and "?" to read the system characteristics and Viessmann's user tips; note the code (e.g. F.xxx) and text for your contractor (operating instructions 6249162 p.57).
- Acknowledge the message once via the HMI; do not acknowledge fault messages several times in quick succession (6249162 p.58) - notify your contractor.
- Check the heat pump breaker/isolator in the consumer unit is ON (do not repeatedly reset a breaker or RCD that keeps tripping).
What the engineer will check
- Check the settings in the commissioning assistant. Adjust settings if required.
- Check connections on M2IO electronics module.
- Check whether components are wrongly connected.
- Isolate the system from the power supply. Restart the system. If the fault persists, replace M2IO electronics module.
Who to ask for: Viessmann-trained heat pump installer/service engineer.
Sources
- Installation and service instructions Vitocal 150-A, AWO(-M)-E-AC/AWO(-M)-E-AC-AF 151.A (6171807, 2021-10) ↗ · 6171807 VSA00001 · page 101 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026