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Mitsubishi P8: pipe temperature error (P-Series)

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

Mitsubishi Electric display

P8

“Pipe temperature error”

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. 20
Technician

Self-check: 8 beeps and blinks. Action table: the pipe temperature is out of the cooling or heating range; detection takes at least 9 minutes in cooling and 27 minutes in heating, and P8 is not detected in drying mode.

What it means

P8 is a check code of Mitsubishi’s P-Series PKA-A and PLA-A EA8 indoor units: “Pipe temperature error”. A wired controller shows “P8”; in self-check with a wireless remote it is 8 beeps and 8 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 unit compares the pipe thermistors with the intake air thermistor (TH1) and sets P8 when the pipe temperature stays out of the range it expects for the mode PKA-A24/30/36KA8 Service Manual TCH115A, p. 15; PKA-A12/18LA1 Service Manual TCH117, p. 15; PLA-A EA8 Service Manual TCH120A, p. 20:

  • Cooling. The check uses the lower of the liquid pipe (TH2) and condenser/evaporator (TH5) readings. P8 is set when the pipe is not in the cooling range 3 minutes after the compressor starts and 6 minutes after it left the range, so detection takes at least 9 minutes. P8 is not detected in drying mode.
  • Heating. Once 10 seconds have passed after the compressor starts and the hot adjustment mode has finished, P8 is set if the condenser/evaporator pipe (TH5) does not reach the heating range within 20 minutes. Detection takes at least 27 minutes, and time spent defrosting is excluded; detection restarts after defrost.

Each range is set by a 5.4°F (3°C) difference between the pipe and intake readings. Because of these delays, P8 can appear well after the unit was switched on.

Causes listed: too small a difference between room temperature and the pipe thermistor readings, from a refrigerant shortage, a pipe thermistor holder that has come off, or a defective refrigerant circuit; extension pipes or indoor/outdoor connecting wires connected the wrong way round on systems with several indoor units; faulty readings from the room or pipe thermistors; and a stop valve that is not fully open PKA-A24/30/36KA8 Service Manual TCH115A, p. 15.

On M-Series MSZ wall units, the indoor lamp table has no 8-blink row MSZ-GL Indoor Service Manual OBH732D, p. 27. 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.

When to call a licensed technician

  • The technician compares the pipe temperatures with the room temperature shown on the remote controller and on the outdoor controller circuit board, using the board’s SW2 setting and the A-Control Service Tool PAC-SK52ST PKA-A24/30/36KA8 Service Manual TCH115A, p. 15.
  • On systems with several indoor units, the table has the technician check for reversed extension pipe connections and reversed indoor/outdoor connecting wires PKA-A24/30/36KA8 Service Manual TCH115A, p. 15.
  • A refrigerant shortage or a stop valve that is not fully open is refrigerant-side work. It 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 P8 detection rules and causes. TCH117 says “reverse” where TCH115A says “converse” PKA-A12/18LA1 Service Manual TCH117, p. 15.
  • P6, “Freezing/Overheating protection operation”, uses the same pipe thermistors with fixed temperature limits instead of a difference from the room temperature PKA-A24/30/36KA8 Service Manual TCH115A, p. 15.

Related Mitsubishi Electric codes

  • P6 “Freezing/Overheating protection operation”
  • 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. 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.