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Mitsubishi P6: freezing or overheating protection (P-Series)

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

Mitsubishi Electric display

P6

“Freezing/Overheating protection operation”

PKA-A KA8, PKA-A LA1, PLA-A EA8 · TCH115A (PKA-A KA8) p. 12; TCH115A (PKA-A KA8) p. 15; TCH117 (PKA-A LA1) p. 12; TCH117 (PKA-A LA1) p. 15; TCH120A (PLA-A EA8) p. 16; TCH120A (PLA-A EA8) p. 19
Technician

Self-check: 6 beeps and blinks. Action table: the pipe temperature stays below −5°F (−15°C) in cooling or rises above 158°F (70°C) in heating, and does so again after a 6-minute resume prevention period.

What it means

P6 is a check code of Mitsubishi’s P-Series PKA-A and PLA-A EA8 indoor units: “Freezing/Overheating protection operation”. A wired controller shows “P6”; in self-check with a wireless remote it is 6 beeps and 6 blinks 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 code is based on the pipe temperature (liquid pipe or condenser/evaporator), with two triggers PKA-A24/30/36KA8 Service Manual TCH115A, p. 15; PKA-A12/18LA1 Service Manual TCH117, p. 15; PLA-A EA8 Service Manual TCH120A, p. 19:

  • Freezing protection in cooling. Starting 3 minutes after the compressor starts, if the pipe stays under −5°F (−15°C) for 3 minutes, the unit enters a 6-minute resume prevention mode. P6 is set if the pipe stays under −5°F (−15°C) for 3 minutes again within 16 minutes after that.
  • Overheating protection in heating. If the pipe goes over 158°F (70°C) after the compressor starts, the unit enters the 6-minute resume prevention mode. P6 is set if it goes over 158°F (70°C) again within 30 minutes after that.

The causes listed for cooling or drying are a clogged filter (reduced airflow), a short cycle of the air path, low-load (low temperature) operation outside the tolerance range, a defective indoor fan motor or indoor controller board, defective outdoor fan control, an overcharge of refrigerant and a refrigerant circuit with clogs. For heating, the list has over-load (high temperature) operation in place of low-load, plus a defective bypass circuit in the outdoor unit PKA-A24/30/36KA8 Service Manual TCH115A, p. 15.

On M-Series MSZ wall units, 6 blinks of the indoor lamp means “Outdoor thermistors” MSZ-GL Indoor Service Manual OBH732D, p. 27, and 6 blinks of the outdoor board LED means “Serial signal” MUZ-GL Outdoor Service Manual OBH733J, p. 46. The P-Series table does not apply to them.

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. Check the error status, stop the operation and consult your dealer PAR-40MAAU Instruction Book, p. 65.
  2. If the code shows on the main display while the indoor unit keeps running, check the code and consult your dealer PAR-40MAAU Instruction Book, p. 9.
  3. F4 or the ON/OFF button resets the error that is occurring, unless ON/OFF operation is prohibited PAR-40MAAU Instruction Book, p. 66. The book does not say a reset fixes the cause.

The first cause the service manual lists for both modes is a clogged filter. Without a PKA-A or PLA-A owner’s manual, this page gives no filter-cleaning steps.

When to call a licensed technician

The action table’s countermeasures, in the order printed PKA-A24/30/36KA8 Service Manual TCH115A, p. 15; PLA-A EA8 Service Manual TCH120A, p. 19:

  • Check the filter for clogs.
  • “Remove shields.” This answers the short-cycled air path.
  • Check the indoor fan motor and board under section 9-6, “How to check the parts”.
  • Check the outdoor fan motor.
  • Check the operating condition of the refrigerant circuit, which covers the overcharge, clog and bypass circuit causes. Refrigerant work is for a technician certified under EPA Section 608.

The warning box on this page is quoted from an M-Series owner’s manual.

Notes for different models

  • The three P-Series manuals print the same P6 triggers and causes. TCH117 gives the temperatures in °C first, −15°C [−5°F] and 70°C [158°F] PKA-A12/18LA1 Service Manual TCH117, p. 15.
  • P8, “Pipe temperature error”, is a separate code on the same units that also uses the pipe thermistors PKA-A24/30/36KA8 Service Manual TCH115A, p. 15.

Related Mitsubishi Electric codes

  • P8 “Pipe temperature error”
  • P2 “Pipe (TH2) sensor error”
  • P9 “Pipe (TH5) sensor error”

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 Corporation. MUZ-GL Outdoor Service Manual OBH733J. No. OBH733, Revised Edition-J, issued Jun. 2021; covers MUZ-GL09–24NA and NAH, MUY-GL09–24NA (the cover lists no MUZ-GL06). Copy hosted by a Mitsubishi distributor (Gemaire/Baker Distributing).. Accessed Oct 12, 2026.
  3. 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.
  4. Mitsubishi Electric Corporation. PKA-A24/30/36KA8 Service Manual TCH115A. No. TCH115, Revised Edition-A, August 2023. Accessed Oct 12, 2026.
  5. Mitsubishi Electric Corporation. PKA-A12/18LA1 Service Manual TCH117. No. TCH117, March 2023. Accessed Oct 12, 2026.
  6. 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.