Mitsubishi Electric P1

What does Mitsubishi Electric P1 mean?

The indoor unit detected an intake sensor error, shown as P1 on the wired controller. The intake (room-air) thermistor reads the air entering the indoor unit so the system can control temperature; an open, shorted, or out-of-range reading produces this code. The fault is in the sensor or its wiring on the indoor side, not in the outdoor refrigerant circuit.

Symptoms

• P1 displayed on the wired controller
• Indoor unit stops or runs erratically
• Poor temperature control before the fault
• Code recurs after restart

Common causes

• Disconnected or loose intake thermistor connector
• Open circuit from damaged sensor wiring
• Shorted intake thermistor element
• Corrosion or moisture at the indoor sensor connector

Diagnostic steps

1. 01

   Power down the indoor unit

   Switch off power before opening the indoor unit to inspect the sensor.

2. 02

   Check the intake sensor connector

   Verify the intake thermistor is plugged in and the connector is clean and seated.

3. 03

   Inspect the wiring

   Trace the sensor lead for cuts, pinches, or chafing that could open the circuit.

4. 04

   Dry any moisture

   Clean and reseat the connector if it shows corrosion or water ingress.

5. 05

   Restart and confirm

   Restore power and check whether P1 clears once the connection is secure.

When to call a professional

Call a technician if P1 persists after the connector is reseated, since confirming an open or shorted thermistor requires resistance testing against the service data. Replacing the intake sensor means working inside the indoor unit near the control board. A qualified professional should verify and replace the faulty thermistor.