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E6

E6 - Indoor/Outdoor communication error

Mitsubishi Electric · Air Conditioning

What does E6 mean?

This error occurs when the Ecodan unit is powered on before the FTC(2) unit, leading to an indoor/outdoor communication failure.

Common Causes

  • Ecodan powered on before FTC(2)
  • Communication wiring fault
  • Incorrect power sequence

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Ensure the FTC(2) unit is powered on before the Ecodan unit.

  2. 2

    Check the communication wiring between the units.

  3. 3

    Reset power to both units in the correct sequence.

  4. 4

    Verify connections on the main boards.

Browse all codes in this manual (177)
Verified technical data. Last updated: April 2026

Related Faults

0.5-second ON / 0.5-second OFF blinkUpper lamp blinks 0.5-second ON/OFF - Miswiring or serial signal error0.5s blink with beepLeft OPERATION INDICATOR lamp blinks every 0.5 seconds with a beep — Indoor or outdoor unit abnormality00Normal operation - No error codes
Source: Mitsubishi Electric Air Conditioning
Open Manual (Page 35)Search more codes in this manual