- HVAC
- Air conditioner
P2
Mitsubishi Electric P2 on an air conditioner: pipe sensor error
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Mr. Slim PKA wall-mounted splits, P2 means the liquid pipe thermistor (TH2) reads an impossible value, like an open or short circuit. Do one reset from the breaker; if P2 returns, call a technician without opening the unit.
Safety first
Stop and check this first
- Mitsubishi Electric requires all supply circuits to be disconnected before accessing terminals. Do not open the indoor unit casing or the outdoor unit panels: measurements on the board and sensor are technician work.
- If refrigerant leaks, the manual says to ventilate the room: in contact with a flame, the refrigerant releases poisonous gases.
Safe checks you can perform
- Read the code with the remote
- One reset from the breaker
- Thermistor and connector measurement
- Pipe temperature in test run mode
Leave these tasks to a qualified professional
- Do not attempt this professional task: Thermistor check against the table
- Do not attempt this professional task: Temperature reading in test run mode
- Do not attempt this professional task: R410A circuit check when needed
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Thermistor check against the table
What they doThe technician measures the TH2 resistance and inspects its connector and wiring before replacing anything.
They must show youthe measured resistance compared with Mitsubishi Electric's table and the reference temperature.
In writingcode P2, measured values, connector condition and any part replaced with the reason.
Temperature reading in test run mode
What they doIf the sensor is good, they read the pipe temperature in test run mode to rule out a circuit or board fault.
They must show youthe pipe temperature on the remote during the test and the real temperature.
In writingreadings, mode used, final diagnosis and date.
R410A circuit check when needed
What they doWith extreme readings, a certified technician checks the circuit with a leak detector and, if needed, recovers and charges the specified amount.
They must show youthe measured pressures and the leak detector result.
In writingleak test result and kg of R410A recovered or charged, if the circuit was opened.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Read the code with the remote
- Who:
- you, with the unit's wireless or wired remote controller.
- How:
- with the wireless remote, Mitsubishi Electric describes pressing CHECK twice, choosing the address with TEMP and pressing HOUR while pointing at the unit; with a fault, the operation lamp blinks and a buzzer sounds. P2 is 2 blinks. Press ON/OFF to leave check mode.
- Result that matters:
- confirming the code is P2 (2 blinks) and not P1 or P9, which point to other sensors.
- If you see P2 or 2 blinks:
- continue with this page.
- If you see another code:
- check its own page, because the manual separates each sensor.
- Evidence to keep:
- a photo or video of the remote or the blinking lamp, and the date.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
One reset from the breaker
- Who:
- you, at the consumer unit or the unit's isolator.
- How:
- switch the unit off with the remote, turn off the breaker, wait until everything is off and turn it back on. Mitsubishi Electric says to turn the power off and on again to operate after the checks; do not repeat it several times.
- Result that matters:
- whether the code comes back once the unit is running again.
- If P2 does not return:
- note the episode; the unit returns to normal when the sensor recovers, but have it checked if it repeats.
- If P2 returns:
- leave the unit off and call a technician; do not keep resetting.
- Evidence to keep:
- the date, time, mode in use and whether the code returned and after how long.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Thermistor and connector measurement
- Who:
- a qualified air conditioning technician.
- How:
- with the power isolated, measure the TH2 thermistor resistance and compare it with the manual's table (for example 15.0 kΩ at 0 °C, 6.3 kΩ at 20 °C, 3.0 kΩ at 40 °C), flexing the lead to find breaks, and inspect the connector on the indoor board.
- Result that matters:
- whether the fault is in the sensor, its wiring or connector, or elsewhere.
- If the resistance is off or changes when the lead is flexed:
- the sensor is replaced or the connection repaired.
- If the sensor measures correctly:
- the technician checks the pipe temperature in test run mode and the board.
- Evidence to keep:
- measured values, the temperature at which they were taken and the connector condition.
Requires access to the controller board inside the indoor unit with the power isolated: technician only.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Pipe temperature in test run mode
- Who:
- an F-gas certified air conditioning technician.
- How:
- puts the unit in test run mode and reads the liquid pipe temperature on the remote. Mitsubishi Electric says a very low reading in cooling or a very high one in heating points to a refrigerant circuit problem.
- Result that matters:
- telling an electrical sensor fault apart from an R410A circuit problem.
- If the reading is extreme but consistent:
- the refrigerant circuit is checked with gauges and a leak detector.
- If the reading does not match the real temperature:
- the manual points to the indoor controller board.
- Evidence to keep:
- test run readings, operating mode and outdoor temperature.
The circuit uses high-pressure R410A; gauges, recovery and charging are work for a certified technician only.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- HVAC
- Brand
- Mitsubishi Electric
- Product type
- Air conditioner
Known code variants
- deshumidificador Midea P2 cubo lleno
- Midea dehumidifier P2 bucket full
- Midea MAD50 P2
- Midea P2
- Mitsubishi Electric P2
- Mitsubishi P2
- Mr. Slim P2
- P 2
- PKA P2
What it means
In service manual OCH639 for the PKA-A24/30/36KA7 indoor units, Mitsubishi Electric links P2 to a pipe (TH2) sensor error: the unit enters a 3-minute restart delay when it detects a short (90 °C or more) or an open circuit (-40 °C or less) and flags the error if it does not recover by itself. The manual also links it to a faulty refrigerant circuit pushing the pipe to those temperatures. Other models may use the code differently. The code alone never proves that a specific part is faulty.
Warnings and stop conditions
- Higheditorial warning
Mitsubishi Electric requires all supply circuits to be disconnected before accessing terminals. Do not open the indoor unit casing or the outdoor unit panels: measurements on the board and sensor are technician work.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Mediumsource verified
If refrigerant leaks, the manual says to ventilate the room: in contact with a flame, the refrigerant releases poisonous gases.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Symptoms and causes
Probable causes · in order
- TH2 thermistor off its curveCommon
Mitsubishi Electric lists defective thermistor characteristics first, which are checked by measuring its resistance.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Sensor connector or wiringCommon
Poor contact of the sensor connector on the indoor controller board, or a broken wire or poor contact in the thermistor wiring.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Refrigerant circuit at an extreme temperaturePossible
The manual says a defective refrigerant circuit can push the pipe to 90 °C or more, or -40 °C or less, and trigger P2 even with a good sensor.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
- Indoor controller boardPossible
If the pipe reading in test run mode is far from the real temperature, Mitsubishi Electric says to replace the indoor controller board.
Evidence: Mitsubishi Electric split-system heat pump service manual OCH639, indoor units PKA-A24KA7, PKA-A30KA7, PKA-A36KA7
Virtual technician
Does P2 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Mitsubishi Electric · 2016 · manual
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