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Mitsubishi E6: indoor/outdoor communication error (P-Series)

By How House Works EditorialBased on Mitsubishi Electric manualsChecked against sources Updated

Mitsubishi Electric display

E6

“Indoor/outdoor unit communication error”

PKA-A KA8, PKA-A LA1, PLA-A EA8 · TCH115A (PKA-A KA8) p. 12; TCH115A (PKA-A KA8) p. 17; TCH117 (PKA-A LA1) p. 12; TCH117 (PKA-A LA1) p. 17; TCH120A (PLA-A EA8) p. 16; TCH120A (PLA-A EA8) p. 22
Technician

Self-check: 3 beeps and blinks, shared with E7. Action table: signal receiving error; the indoor controller board cannot receive any signal normally for 6 minutes after power-on, or for 3 minutes.

What it means

E6 is a check code of Mitsubishi’s P-Series PKA-A indoor units (KA8 and LA1) and PLA-A EA8 indoor units. A wired controller shows “E6”. In self-check with a wireless remote it is 3 beeps and 3 blinks of the OPERATION INDICATOR lamp, the same count as E7 PKA-A24/30/36KA8 Service Manual TCH115A, p. 12; PKA-A12/18LA1 Service Manual TCH117, p. 12; PLA-A EA8 Service Manual TCH120A, p. 16.

The self-diagnosis action table calls E6 a signal receiving error. It is set when the indoor controller board cannot receive any signal normally for 6 minutes after the power is turned on, or for 3 minutes. With 2 or more indoor units on one outdoor unit, it is also set when the indoor board goes 3 minutes without the signal from the outdoor controller board that lets the outdoor board transmit PKA-A24/30/36KA8 Service Manual TCH115A, p. 17; PLA-A EA8 Service Manual TCH120A, p. 22.

The causes the table lists: a contact failure, short circuit or miswiring (reversed wiring) of the indoor/outdoor connecting wire, a defective transmitting and receiving circuit on the indoor controller board, and electrical noise on the connecting wire PKA-A24/30/36KA8 Service Manual TCH115A, p. 17.

Not every wait is an E6. The service manual says that for about 3 minutes after power-on the remote controller cannot be used while the system starts up, and calls this correct operation PKA-A24/30/36KA8 Service Manual TCH115A, p. 13.

E6 comes from the P-Series service manuals only. The M-Series wall units in this set (MSZ-GL, FS, FH, GS) report faults as blinks, and none of their manuals here has an E6 table. Their indoor lamp row for a lost signal from the outdoor unit is a steady 0.5-second blink, “Miswiring or serial signal” MSZ-GL Indoor Service Manual OBH732D, p. 27.

Check these first

The owner’s manuals for PKA-A and PLA-A units are not among our sources. If your wired controller is a PAR-40MAAU, its instruction book gives these steps:

  1. When an error occurs, the controller shows an error screen and its operation LED blinks. The book says to check the error status, stop the operation and consult your dealer PAR-40MAAU Instruction Book, p. 65.
  2. The error screen shows the error code, the unit, the refrigerant address and the date and time, plus the model name, serial number and dealer’s phone number if they were registered PAR-40MAAU Instruction Book, p. 65.
  3. If the code shows on the main display while the indoor unit keeps running, the book says to check the code and consult your dealer PAR-40MAAU Instruction Book, p. 9.
  4. The book says F4 or the ON/OFF button resets the error that is occurring, unless ON/OFF operation is prohibited PAR-40MAAU Instruction Book, p. 66. It does not say a reset fixes the cause.

When to call a licensed technician

  • The technician reads the LED display on the outdoor control circuit board with the A-control service tool PAC-SK52ST, following the outdoor unit’s service manual PKA-A24/30/36KA8 Service Manual TCH115A, p. 17.
  • The table then has the technician check the indoor/outdoor connecting wire at both units for disconnection or looseness, and every unit in a twin or triple system. If the fault returns after the power is switched off and on, the indoor controller board or the outdoor controller circuit board is replaced PKA-A24/30/36KA8 Service Manual TCH115A, p. 17.
  • For a unit that cannot be operated after the test run, the start-up table lists incorrect polarity of the S1, S2 and S3 wiring between the indoor and outdoor units among the causes PKA-A24/30/36KA8 Service Manual TCH115A, p. 13.
  • The warning box on this page is quoted from an M-Series owner’s manual.

Notes for different models

  • PKA-A12/18LA1 prints the same E6 row on p. 17 of its manual, with “reverse wiring” where TCH115A says “converse wiring” PKA-A12/18LA1 Service Manual TCH117, p. 17.
  • E7, the other 3-blink code, is a transmitting error: the indoor board receives “1” 30 times in a row although it sent “0” PKA-A24/30/36KA8 Service Manual TCH115A, p. 17.
  • E9 is a different signal: output pattern B, detected by a unit other than the indoor unit PKA-A24/30/36KA8 Service Manual TCH115A, p. 12. The action table does not cover codes detected in the outdoor unit and refers to the outdoor unit’s service manual, which is not among our sources PKA-A24/30/36KA8 Service Manual TCH115A, p. 14.

Related Mitsubishi Electric codes

  • E7 “Indoor/outdoor unit communication error”
  • E9 “Indoor/outdoor unit communication error (Transmitting error) (Outdoor unit)”
  • EE “Combination error between indoor and outdoor units”

See also

Other ductless mini-splits: Daikin, Fujitsu, MrCool

All Mitsubishi Electric codes

Mitsubishi Electric is a trademark of its owner. How House Works is not affiliated with or endorsed by Mitsubishi Electric.

Sources

  1. Mitsubishi Electric Corporation. MSZ-GL Indoor Service Manual OBH732D. No. OBH732, Revised Edition-D, issued Feb. 2022; covers MSZ-GL06–24NA and MSY-GL09–24NA. Accessed Oct 12, 2026.
  2. Mitsubishi Electric. PAR-40MAAU Instruction Book. Printed code WT09033X01; MA remote controller for CITY MULTI, M-series and P-series air conditioners. Accessed Oct 12, 2026.
  3. Mitsubishi Electric Corporation. PKA-A24/30/36KA8 Service Manual TCH115A. No. TCH115, Revised Edition-A, August 2023. Accessed Oct 12, 2026.
  4. Mitsubishi Electric Corporation. PKA-A12/18LA1 Service Manual TCH117. No. TCH117, March 2023. Accessed Oct 12, 2026.
  5. Mitsubishi Electric Corporation. PLA-A EA8 Service Manual TCH120A. No. TCH120, Revised Edition-A, August 2023; covers PLA-A12/18/24/30/36/42/48EA8. Accessed Oct 12, 2026.