Try DIY first — may need a proVerified by FixOffice
Mitsubishi E6 — Indoor/outdoor unit communication error
Applies to: Mr. Slim / M-Series mini-splits
What this error means
The indoor head and outdoor unit stopped communicating. Causes range from a power blip to wiring faults between units, or a failing control board. On Mr. Slim systems this is one of the most common fault codes.
Symptoms
- E6 on the wall controller or blinking indoor unit lights
- Unit stops heating/cooling
- May recur after resets
Try this first (safe DIY steps)
- Kill power to the system at the breaker/disconnect for 3–5 minutes, then restore — a genuine full power cycle clears transient comm faults
- Check the outdoor unit's disconnect and breaker haven't tripped
- Note whether it recurs and how quickly — that pattern is gold for the technician
Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.
When to call a technician
On recurrence — inter-unit wiring and board diagnosis is technician territory (high voltage present).