Error codes · Mitsubishi
Mitsubishi Mini-Split E6 / Communication Error
E6 (and related communication codes) means the indoor head and outdoor unit are not talking cleanly over the control pair. Many cases are loose terminal screws or damaged conductor — not an automatic board replacement.
Updated July 2026 · 5 min read · United States
Symptoms
- Indoor display shows E6 / communication error
- Outdoor unit may not start
- Error appears after storms or service work
Likely causes
- Loose S1/S2/S3 (or A/B) terminal screws
- Damaged interconnect cable
- Incorrect wire landing after a thermostat/controller swap
- Failed indoor or outdoor control board
What to do
1. Power down indoor and outdoor
Shut breakers for both units before opening electrical covers.
2. Reseat interconnect terminals
Tighten the control conductors on the outdoor terminal block. Look for corrosion or aluminum/copper issues.
3. Inspect cable for staples or cuts
Damaged sheathing between heads and the condenser is a frequent post-renovation cause.
Stop and call a pro when
- Terminals are tight and cable looks intact
- Multiple indoor heads fault together on a multi-zone
- You need board-level diagnostics
Related guides
- Trane Code 126 — Trane communicating code 126 outdoor fan faults: what homeowners can check safely, capacitor symptoms, and when the condenser needs a technician.
- Nest C-Wire Install — Step-by-step Nest Learning Thermostat C-wire guidance: how to tell if you need a common wire, power connector options, and Rh/Rc/W/Y/G labeling.
FAQ
Will resetting the breaker clear E6 permanently?
A reset may clear a temporary glitch, but recurring E6 needs wiring or board repair.
Need a licensed tech instead?
If the guide says to stop — or the part swap did not clear the fault — get free quotes from licensed local HVAC contractors.
Get matched with a pro