What it means
Mitsubishi's trigger points: in cooling, pipe temperature below -15°C (5°F) for 3 minutes after the compressor starts; in heating, above 70°C (158°F). The unit first pauses for 6 minutes before it tries again. With a wireless remote, the self-check reports it as 6 beeps and 6 flashes (SLZ-KF, SLZ-M and SEZ-KD manuals).
What to check, in order
- Clean the air filters
Mitsubishi lists a clogged filter that reduces airflow as a cause. Switch off and clean the filters as your operation manual shows.
- Clear the air path
Short cycling, where the unit's own air is drawn straight back in, is also on Mitsubishi's list. Move anything blocking the indoor unit's air inlet or outlet.
- Let it restart
After the code, switch off at the breaker and back on and run it again. If P6 returns, note it for the engineer.
When to call an engineer
If it keeps happening, call an F-gas certified engineer (UK) or HVAC technician (US). Mitsubishi lists a faulty indoor fan motor or indoor control board, faulty outdoor fan control, too much refrigerant, a restricted refrigerant circuit, running outside the unit's load range and, in heating, a faulty bypass circuit in the outdoor unit.
Quick answers
What does the Mitsubishi P6 error code mean?
The indoor coil got too cold while cooling or too hot while heating, so the unit has stopped to protect itself. Mitsubishi's trigger points: in cooling, pipe temperature below -15°C (5°F) for 3 minutes after the compressor starts; in heating, above 70°C (158°F). The unit first pauses for 6 minutes before it tries again. With a wireless remote, the self-check reports it as 6 beeps and 6 flashes (SLZ-KF, SLZ-M and SEZ-KD manuals).
Can I fix Mitsubishi P6 myself?
Easy (about 20 minutes). Start with: clean the air filters; clear the air path; let it restart. If it keeps happening, call an F-gas certified engineer (UK) or HVAC technician (US). Mitsubishi lists a faulty indoor fan motor or indoor control board, faulty outdoor fan control, too much refrigerant, a restricted refrigerant circuit, running outside the unit's load range and, in heating, a faulty bypass circuit in the outdoor unit.
Is Mitsubishi P6 worth repairing?
Worth fixing. Clean filters and a clear air path cost nothing. If that doesn't stop it, a fan or refrigerant fault needs an engineer.
Checked against
- Mitsubishi Electric SLZ-KF09/12/15/18NA1 ceiling cassette (M-series) Technical & Service Manual TCH118A (PDF)
- Mitsubishi Electric SLZ-M15-60FA ceiling cassette Technical & Service Manual OCH522 (PDF)
- Mitsubishi Electric SEZ-KD09/12/15/18NA(4) ducted (M-series) Technical & Service Manual HWE0802B (PDF)
- Mitsubishi Electric PCA-M35-140KA indoor unit Service Manual OCH659 (PDF)
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.