What does Mitsubishi Electric error code E6 mean?

E6 on Mitsubishi Electric split systems and City Multi VRF indicates a communication fault between the indoor and outdoor units. Check the inter-unit wiring on the S1, S2, S3 terminals (S1=common, S2=power, S3=signal). Verify correct polarity and check for damaged cable insulation. Also confirm the outdoor unit has power before the indoor unit is tested.

How do I put a Mitsubishi Electric City Multi system into service mode?

To enter service mode on a Mitsubishi City Multi outdoor unit, press and hold the SW01 (check/test) button on the main PCB for 5 seconds. In service mode, you can view refrigerant temperatures, pressures (if sensors fitted), expansion valve positions, and operating frequencies on the PCB LED display. Use the Mitsubishi G-50A or AE-200 central controller for comprehensive system diagnostics.

What does Mitsubishi error code P5 indicate?

P5 on Mitsubishi split systems indicates a drain pump fault or overflow at the indoor unit condensate tray. Check the condensate tray float switch operation — the float switch triggers when the tray is full. Clear any blockages in the condensate drain pipe, verify the drain is sloped correctly, and test the drain pump operation. Reset the fault by turning the system off and back on after clearing the drain.

How do I check the refrigerant charge on a Mitsubishi Electric VRF system?

Mitsubishi Electric VRF systems require precise refrigerant charge per the installation manual based on pipe lengths and number of indoor units. Use the Mitsubishi charge calculator to determine the correct charge for your system configuration. Connect low-side and high-side gauges to the service ports, operate in cooling mode at full load, and verify pressures and subcooling/superheat against the Mitsubishi target values at the current outdoor temperature.

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By Octavian Ghindea

Co-founder & CTO · Reviewed May 2026

What error codes does Mitsubishi Electric display?

Inter-unit communication fault — check S1/S2/S3 wiring

Drain pump fault or condensate overflow

High pressure protection — check condenser coil and fans

Indoor/outdoor unit mismatch or pairing error

Reverse phase or power imbalance on 3-phase units

Common questions about Mitsubishi Electric equipment

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