Pipe Temperature 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 pipe temperature is not changing as it should during operation: the unit calls for cooling but the difference between pipe and intake air temperature stays too small. The unit stops because this shows cooling is not actually reaching the coil. 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: P2P6U2E6

Symptoms4

• The fan runs but the air comes out at or near room temperature.
• The unit stops after several minutes of running and P8 appears.
• The outdoor unit sometimes runs without the room getting cooler.
• The code appears after a new installation or after the unit was moved.

Possible causes5

• A serious refrigerant shortage from a leak.
• Service valves on the outdoor unit closed or only partly open after installation.
• The TH2 sensor off the pipe, reading air temperature instead of pipe temperature.
• On multi systems, one indoor unit piped or wired to another unit's port.
• A faulty electronic expansion valve, or the outdoor compressor not starting.

How to diagnose5

1. Switch off at the breaker for a few minutes, restart in cooling, and see whether the outdoor unit runs.
2. Check that the outdoor unit is clean, its fan turns, and its breaker is on.
3. The technician confirms the service valves are fully open and, on multi systems, that piping and wiring match between units.
4. The technician measures refrigerant pressures and pipe temperatures and compares them with the manufacturer specification to detect undercharge.
5. The technician confirms TH2 is fixed to the pipe and compares its reading with the real pipe temperature.

How to fix6

1. Open the service valves fully if they were closed.
2. Refit the TH2 sensor on the pipe, or replace it if faulty.
3. Correct piping and wiring on multi systems.
4. Have a licensed technician repair the leak and recharge refrigerant by weight.
5. Repair the electronic expansion valve or inspect the outdoor unit if the compressor does not run.
6. Run in cooling, watch the pipe temperature, and confirm the code is gone.

Repair cost

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

The cost is low for a closed valve or a displaced sensor, and rises for a leak repair with recharge or an expansion valve replacement.

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