What It Means
General transmission line communication failure between indoor and outdoor units.
Mitsubishi Electric All Systems
Mitsubishi Electric Error Code EE
Troubleshooting guide for the Mitsubishi Electric system fault EE.
Possible Causes
- Loose, corroded, or reversed transmission line terminal connections.
- Damaged, pinched, or water-intruded communication cable.
- Electrical noise interference from nearby high-voltage wiring.
- Indoor unit address or wiring conflicts on shared outdoor bus.
- Failed indoor or outdoor control board transmission circuit.
Not sure which one it is — or if it's none of these? Try ACLogics today.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis
Error detail: this is a general indoor/outdoor communication fault raised when the transmission line between the indoor unit(s) and the outdoor unit loses signal integrity, distinct from the more granular E6/E7/E8/E9 codes that pinpoint whether the failure is on the indoor or outdoor side and whether it is a receiving or transmitting fault. Because the indoor and outdoor boards can no longer exchange operating data, the system halts normal operation and the outdoor unit drops compressor and fan output until communication is restored. EE typically points to a shared bus problem (wiring, connector, electrical noise) affecting the whole system rather than a single indoor unit's sensor, which would instead trigger a P-series thermistor code.
All Recorded Causes
Loose, corroded, or reversed transmission line connections at the indoor or outdoor terminal blocks. Damaged, pinched, or water-intruded communication cable. Electrical noise from nearby high-voltage wiring or ungrounded equipment interfering with the signal. Address or wiring conflicts when multiple indoor units share one outdoor unit. Failed indoor or outdoor control board transmission circuit. Cable length or gauge exceeding manufacturer spec, degrading the signal.
Verify Before Replacing Parts
- Confirm the exact Mitsubishi Electric model family and default context before acting on a generic code description.
- Confirm board LEDs, wiring polarity, and model compatibility before replacing control boards — this Mitsubishi Electric fault points at loose, corroded, or reversed transmission line connections at the indoor or outdoor termin….
- Check for intermittent communication faults caused by connectors, moisture, or damaged harnesses, and rule out damaged, pinched, or water-intruded communication cable.
- After the correction, run the system long enough to confirm the default fault does not return under normal load.
Not sure which system this Mitsubishi Electric code is on?
ACLogics has guided diagnostics for 73 Mitsubishi Electric fault codes and asks the right questions to narrow it down.
