How House Works

MrCool P6: the meaning depends on your series

By How House Works EditorialBased on MrCool manualsChecked against sources Updated

MrCool display

P6

“Discharge temp sensor”

DIY E Star 3rd Gen · DIY E Star 3rd Gen Installation & Owner's Manual, p. 39
Owner checks, then technician

No LED pattern printed for this row. P6 means other things in other MrCool documents: “High pressure protection or low pressure protection(for some models)” in the Advantage 4th Gen service manual's letter table (Advantage 4th Gen Service Manual, Troubleshooting p. 4), and in the DIY 4th Gen multi-zone guide the description of PC 00, IPM malfunction, begins “PC 00/(ODU)P6” (DIY 4th Gen Multi-Zone Troubleshooting & Solutions Guide, Troubleshooting p. 36).

What it means

P6 has three different meanings in MrCool’s documents. The box above shows the DIY E Star 3rd Gen meaning; find your series before you act on any of them.

  • DIY E Star 3rd Gen: “Discharge temp sensor”. The table prints no LED pattern for this row DIY E Star 3rd Gen Installation & Owner’s Manual, p. 39. The same table also has F3, “Compressor discharge temperature sensor T5 open circuit or short circuit”, with 4 operation LED flashes and the timer LED on; the manual does not explain how P6 differs from F3.
  • Advantage 4th Gen: the service manual’s letter-code table gives P6 as “High pressure protection or low pressure protection(for some models)”, with 7 operation lamp flashes and the timer lamp flashing Advantage 4th Gen Service Manual, Troubleshooting p. 4. Its section headed “P6/PC 03” says the outdoor pressure switch cut off the system because high pressure was above 4.4 MPa or low pressure below 0.13 MPa Advantage 4th Gen Service Manual, Troubleshooting p. 35. PC 03 is the code the DIY 4th and 5th Gen manuals use for pressure protection.
  • DIY 4th Gen multi-zone: the troubleshooting guide’s description of PC 00 begins “PC 00/(ODU)P6”, where the voltage signal the IPM sends to the compressor drive chip is abnormal and the unit turns off DIY 4th Gen Multi-Zone Troubleshooting & Solutions Guide, Troubleshooting p. 36. The guide pairs P6 on the outdoor unit with PC 00; the same generation’s outdoor unit table prints the IPM code as PC 00 DIY 4th Gen Multi-Zone Installation & Owner’s Manual, p. 50.

None of the 5th Gen DIY, Select, Easy Pro, Advantage, cassette, multi-zone, hybrid air handler or Olympus code tables prints P6; their codes take the EH, EL, EC and PC form DIY 5th Gen Single-Zone Installation & Owner’s Manual, pp. 39–40.

Check these first

  1. Identify the series from the model number. The 3rd Gen E Star manual lists outdoor units such as DIY-24-HP-C-230B DIY E Star 3rd Gen Installation & Owner’s Manual, p. 21; the Advantage 4th Gen manual lists outdoor units such as A-09-HP-C-115C and A-12-HP-C-230C Advantage 4th Gen Owner’s and Installation Manual, p. 28.
  2. Follow the restart procedure in your own manual. On the 3rd Gen E Star: wait about 10 minutes, then disconnect and reconnect the power, and if the problem remains, disconnect the power and contact the nearest customer service center DIY E Star 3rd Gen Installation & Owner’s Manual, p. 38. On Advantage 4th Gen: wait about 10 minutes, then disconnect the power, connect it again and turn the unit on, and if the problem persists, disconnect the power and contact your nearest customer service center Advantage 4th Gen Owner’s and Installation Manual, p. 16. The DIY 4th Gen multi-zone manual gives the same steps with “roughly 10 minutes” and adds that you should not attempt the repairs yourself DIY 4th Gen Multi-Zone Installation & Owner’s Manual, p. 49.
  3. When you call, give the model number and a description of what the unit did DIY E Star 3rd Gen Installation & Owner’s Manual, p. 38.

When to call a licensed technician

All three meanings lead to technician work:

  • Discharge temp sensor on the 3rd Gen E Star: the manual gives no repair steps, and no 3rd Gen E Star service manual was found among MrCool’s published documents. The next step is the service call in the manual’s procedure.
  • Pressure protection on Advantage 4th Gen: the parts the service manual lists to prepare are connection wires, the outdoor PCB, refrigerant, the pressure switch and the outdoor fan Advantage 4th Gen Service Manual, Troubleshooting p. 35. Refrigerant work is for a technician certified under EPA Section 608.
  • PC 00/(ODU)P6 in the 4th Gen multi-zone guide: the guide lists connection wires, the IPM module board, the outdoor fan assembly, the compressor, the outdoor PCB, the reactor or inductance and the bridge rectifier DIY 4th Gen Multi-Zone Troubleshooting & Solutions Guide, Troubleshooting p. 36.

The service manuals warn that electricity remains in capacitors even when the power supply is off Advantage 4th Gen Service Manual, Troubleshooting p. 3.

Notes for different models

  • Other letter codes also shift: in the 3rd Gen E Star table P2 is a compressor top temperature protection “(only for 9k,12k models)”, while in the Advantage 4th Gen table P2 is “High temperature protection of IPM module or High pressure protection” DIY E Star 3rd Gen Installation & Owner’s Manual, p. 39; Advantage 4th Gen Service Manual, Troubleshooting p. 4.
  • On DIY 4th and 5th Gen indoor displays, pressure faults show as PC 03 and IPM faults as PC 00 DIY E Star 4th Gen Installation & Owner’s Manual, p. 41; DIY 5th Gen Single-Zone Installation & Owner’s Manual, p. 39.

Related MrCool codes

  • F3 “Compressor discharge temperature sensor T5 open circuit or short circuit”
  • PC 03 “Pressure Protection (low or high pressure)”
  • PC 00 “ODU IPM Module Protection”

See also

Other ductless mini-splits: Daikin, Fujitsu, Mitsubishi Electric

All MrCool codes

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

Sources

  1. MRCOOL. DIY 5th Gen Single-Zone Installation & Owner's Manual. Version Date August 5, 2026; file suffix -01; no document number printed. Cover title: DIY Series Single-Zone Mini-Split System, Installation & Owner's Manual. Accessed Oct 13, 2026.
  2. MRCOOL. DIY E Star 4th Gen Installation & Owner's Manual. Version Date 03-21-23; file suffix -01; no document number printed. Not listed on MrCool's documentation page on 2026-10-13; the file is on MrCool's own file host. It prints the same Version Date as the 3rd Gen E Star manual.. Accessed Oct 13, 2026.
  3. MRCOOL. DIY 4th Gen Multi-Zone Installation & Owner's Manual. Version Date 06-06-2023; file suffix -01; no document number printed. Not listed on MrCool's documentation page on 2026-10-13; the file is on MrCool's own file host.. Accessed Oct 13, 2026.
  4. MRCOOL. DIY 4th Gen Multi-Zone Troubleshooting & Solutions Guide. Version Date 10-22-21; file suffix -01; pages are numbered within the Troubleshooting section, cited as printed (Troubleshooting 4). A technician document. MrCool's documentation page labels it the owner's manual for 4th Gen DIY.. Accessed Oct 13, 2026.
  5. MRCOOL. Advantage 4th Gen Owner's and Installation Manual. Version Date 09-19-23; file suffix -01; no document number printed. Cover title: Advantage Series Owner's Manual + Installation Manual. It has no code table; the codes for this series come from the service manual.. Accessed Oct 13, 2026.
  6. MRCOOL. Advantage 4th Gen Service Manual. Version Date 7/06/22; file suffix -01; cover title Advantage Series Air Handler & Condenser Service Manual; pages are numbered within sections, cited as printed (Troubleshooting 5). It prints two lamp tables: one with letter codes (E1, P4, P6 and so on) and one with EH, EL, EC and PC codes. This table uses the second.. Accessed Oct 13, 2026.
  7. MRCOOL. DIY E Star 3rd Gen Installation & Owner's Manual. Version Date 03-21-23; file suffix -01; no document number printed. Not listed on MrCool's documentation page on 2026-10-13; the file is on MrCool's own file host. The code table's text layer is scrambled, so it was read from the page image.. Accessed Oct 13, 2026.