What it means
Mitsubishi's code tables describe U2 as 'abnormal high discharging temperature / 49C worked / insufficient refrigerant'. The PUZ-HA outdoor manual sets it when the compressor discharge sensor (TH4) reads over 125°C (257°F) or 110°C (230°F) continuously for 5 minutes, among other conditions. With a wireless remote, the self-check reports it as 5 beeps and 5 flashes in the outdoor-fault pattern.
What to check, in order
- Write down the code
Note the code and unit number for the engineer, as Mitsubishi's operation manual asks.
- Don't keep resetting it
Switch it off at the breaker. A shortage of refrigerant is one of the causes, and running the compressor hot again and again doesn't fix that.
When to call an engineer
Call an F-gas certified engineer (UK) or HVAC technician (US). Mitsubishi lists a shortage of refrigerant, a stop valve not fully open, a faulty discharge sensor, control board or expansion valve, and a blocked refrigerant circuit. It tells engineers to check for leaks before adding refrigerant.
A repair visit will usually check the refrigerant charge and the pipe joints for leaks, which needs a qualified refrigeration engineer.
- Note the model and serial number. They're on a label on the side of the indoor unit, and on the outdoor unit.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Quick answers
What does the Mitsubishi U2 error code mean?
The refrigerant leaving the outdoor unit's compressor is running too hot. Mitsubishi links this to a shortage of refrigerant, among other causes. Mitsubishi's code tables describe U2 as 'abnormal high discharging temperature / 49C worked / insufficient refrigerant'. The PUZ-HA outdoor manual sets it when the compressor discharge sensor (TH4) reads over 125°C (257°F) or 110°C (230°F) continuously for 5 minutes, among other conditions. With a wireless remote, the self-check reports it as 5 beeps and 5 flashes in the outdoor-fault pattern.
Can I fix Mitsubishi U2 myself?
Engineer only (engineer visit). Start with: write down the code; don't keep resetting it. Call an F-gas certified engineer (UK) or HVAC technician (US). Mitsubishi lists a shortage of refrigerant, a stop valve not fully open, a faulty discharge sensor, control board or expansion valve, and a blocked refrigerant circuit. It tells engineers to check for leaks before adding refrigerant.
Is Mitsubishi U2 worth repairing?
Get a quote first. If refrigerant is low, a leak has to be found and repaired before the system is recharged. Get a quote first.
Checked against
- Mitsubishi Electric SLZ-KF09/12/15/18NA1 ceiling cassette (M-series) Technical & Service Manual TCH118A (PDF)
- Mitsubishi Electric SLZ-M15-60FA ceiling cassette Technical & Service Manual OCH522 (PDF)
- Mitsubishi Electric SEZ-KD09/12/15/18NA(4) ducted (M-series) Technical & Service Manual HWE0802B (PDF)
- Mitsubishi Electric PUZ-HA30/36NHA4 outdoor unit Service Manual OCH504 (PDF)
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.