HVAC Code Lookup

Mitsubishi Electric Mini-Split Code P1

Soft lockout

Room temperature thermistor (TH1) error. The intake air temperature sensor reads short circuit (194F or more) or open circuit (-40F or less), so the unit cannot measure room temperature.

Manual wording: “Room temperature thermistor (TH1) ... Short: 90C [194F] or more, Open: -40C [-40F] or less”

Documented for: A-Control indoor units (PKA-A, PLA-A, PEAD-A and M-Series with a wired controller)

Likely causes, most common first

  1. Defective thermistor characteristics
  2. Contact failure of connector CN20 on the indoor controller board (insert failure)
  3. Breaking of wire or contact failure of thermistor wiring
  4. Defective indoor controller board

What you can safely check yourself

  • Turn the system off at the breaker, wait one minute, and turn it back on once to see if it resets

When to call a technician

Checking the thermistor resistance and its connector means opening the indoor unit and working at the control board. Call a technician.

A Mitsubishi Electric mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Other Mitsubishi Electric codes