Mitsubishi Electric mini split error code P8
Pipe temperature abnormal (refrigerant circuit).
- TypeFault
- SystemRefrigerant circuit
- Can I fix it?Technician job
What P8 means on a Mitsubishi Electric
The indoor pipe temperature does not match the selected mode: the coil is not getting cold in cooling or hot in heating. Points to the reversing valve, a wiring/piping mix-up on multi-splits, or low charge.
On this platform, P8 is a fault: something has failed or is disconnected and needs diagnosis.
Common causes
- A stuck reversing valve.
- On multi-splits, a zone's piping and wiring landed on different ports.
- Low refrigerant charge.
- A pipe sensor reading wrong.
How to fix it yourself
Do the reset and the visual checks, but the underlying repair needs a technician with a meter and the service manual.
- Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
- Switch between Cool and Heat and listen for the reversing valve at the outdoor unit.
- On a multi-split, confirm each zone's line set and cable go to the same port.
- Anything inside the refrigerant circuit (sensors are fine, but valves, compressors and leaks are not) needs EPA-certified refrigerant handling. That is a technician job.
Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.
When to call a technician
A technician needs gauges and the service manual.
Which Mitsubishi Electric units show P8
This page applies to Mitsubishi Electric M-Series (MSZ), Mr. Slim (PKA/PCA), Hyper-Heating H2i and MXZ multi-zone units. Mitsubishi Electric's own documentation lists P8 as "Pipe temperature abnormal (refrigerant circuit)", the same definition used across the Mitsubishi Electric it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.
Where Mitsubishi Electric shows this code
Wall units without a wired controller signal a fault by blinking the operation indicator lamp; the code itself shows on a wired controller (MHK/PAR series) or on the wireless remote after entering its check mode (see your manual). On the outdoor unit, the control board LEDs blink the same code. P codes are indoor-unit faults, E codes are communication faults, F codes are outdoor-unit faults and U codes are outdoor-unit and compressor faults.
Other Mitsubishi Electric codes
Same part of the system as P8:
P8 on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- Blueridge P8 Inverter heat sink (radiator) overheat protection
- Zone Air P8 Outdoor over- or under-temperature protection
- Trane P8 Outdoor over- or under-temperature protection / Pipe temperature abnormal (refrigerant circuit)
Questions people ask
Can I reset a Mitsubishi Electric P8 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If P8 comes back, the fault is real and needs the checks above.
Is it safe to keep running a Mitsubishi Electric showing P8?
The unit will usually refuse to run, or run with reduced output, until the fault is cleared. Repeated resets do not fix anything and can mask a problem that is getting worse.
What will a technician check for P8?
A technician needs gauges and the service manual. Ask for the measurements, not just a parts quote.
Sources
- Mitsubishi Electric M-Series and Mr. Slim service manuals (self-diagnosis tables)
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.