Intake (Room) Temperature Sensor (TH1) Error

What it means

This code appears on the wired remote of Mitsubishi Electric Mr. Slim ducted, ceiling and cassette units. It means the indoor control board is getting an impossible reading from the intake air thermistor (TH1), usually because the sensor or its lead is open or shorted. The unit stops because it no longer knows the real room temperature. The same code can mean something else on other brands, and wall-mounted Mitsubishi Electric models show errors as lamp blinks with a different meaning.

Models covered: Mitsubishi Electric ducted, ceiling and cassette units (Mr. Slim) with check codes on the wired remote; wall-mounted Mitsubishi Electric models may show errors as lamp blinks with a different meaning.

Related codes: P2P8P6

Symptoms4

• The unit stops shortly after start and P1 shows on the wired remote.
• The code returns right after a restart when the sensor is unplugged or broken.
• The code comes and goes when the connector is loose or corroded.
• Uneven cooling before the code appears if the sensor reading is unstable.

Possible causes5

• The TH1 connector is loose or unplugged from the board after service or cleaning.
• The thermistor itself has failed open or shorted with age.
• The sensor lead is pinched or cut inside the unit, or chewed by rodents in the ceiling.
• Moisture or corrosion at the connector from condensation inside the concealed unit.
• A fault in the sensor input circuit on the indoor board (less common).

How to diagnose5

1. Turn the unit off, switch it off at the breaker for a few minutes, restart, and note whether the code returns at once or later.
2. Note the code and unit address from the wired remote and ask the technician to review the error history.
3. With power off, the technician checks, reseats and inspects the TH1 connector on the board.
4. The technician measures the sensor resistance at room temperature, compares it with the manufacturer table, and flexes the lead while measuring to catch an intermittent break.
5. If the sensor is good and the code stays, the input circuit on the indoor board is checked.

How to fix5

1. Reseat the sensor connector and clean any corrosion from the pins.
2. Repair a cut or pinched lead and route it away from sharp edges.
3. Replace the TH1 thermistor with a genuine part for the model.
4. Replace the indoor control board if its input circuit is proven faulty.
5. Restart the unit and confirm the code is gone and the room temperature holds steady.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low when reseating the connector or replacing the thermistor fixes it, and rises when the indoor unit needs a new control board.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions