Mitsubishi P5 Error Code: Drain Pump Fault & Fix (2026)
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Mitsubishi P5 — quick diagnosis
P5 = drain pump fault. Codes can differ a little by series, so it's worth a glance at your own manual.
| Likely cause | How to spot it | What to do |
|---|---|---|
Clogged drain line | Water backs up; pump can't empty the pan | Clear the drain line (most common fix) |
Failed drain pump | Pump is silent when the unit runs | Technician — pump replacement |
Pump wiring / connector | P5 comes and goes | Technician — check the pump connections |
Float switch tripped | Water sensed in the pan | Clear the drain; free the float |
Dirty drain pan | Slime/algae in the pan | Clean the pan, then flush the line |
If your Mitsubishi is flashing a P5 and you spot water pooling in the indoor unit, here’s the short version: P5 is a drain pump fault. The little pump that empties the condensate pan can’t do its job, so the unit shuts down before water overflows. Nine times out of ten the real culprit isn’t the pump itself — it’s a clogged condensate drain line stopping the water from going anywhere. Less often the pump has actually failed or there’s a wiring problem at the pump. The good news is that clearing the drain is a job most homeowners can handle, and it fixes the majority of P5 codes. Below is how to tell a simple clog from a dead pump, and exactly what to do about each.
What the P5 code means
Every time your mini split cools, it wrings moisture out of the air. That water drips into a drain pan, and a small drain pump lifts it out to the drain line. When the unit senses the pan isn’t emptying — the float switch stays up — it throws P5 and stops, rather than letting water spill onto your floor or the electronics.
Common causes
- A clogged drain line — by far the most common. Algae and dust block the line, the pan fills, and the pump can’t keep up. (Full walkthrough: how to clear a clogged drain line.)
- A failed drain pump — the pump motor has worn out and no longer runs.
- Wiring or connector trouble at the pump — an intermittent P5 is often this.
- A stuck float switch — slime in the pan can jam the float in the “full” position.
How to fix a Mitsubishi P5
- Turn the unit off.
- Clear the drain line. A wet/dry vacuum sealed to the outdoor end of the drain usually sucks the clog straight out. See the full drain-line clearing guide.
- Clean the drain pan — soak up the water and wipe away slime so the float moves freely.
- Power-cycle and listen. Restart and check that the pump hums when the unit runs. If it’s silent — or P5 returns with a clear line — the pump needs a pro.
If water is also dripping from the indoor unit, our guide to a leaking mini split covers the related symptoms.
When to call a professional
Seeing a different code? The full Mitsubishi error-code list runs through the rest.
Sources
- Mitsubishi Electric troubleshooting documentation — P5 drain pump / drain overflow diagnostics. Confirm the exact code list for your model number.
Trademark note: “Mitsubishi” and “Mr. Slim” are trademarks of Mitsubishi Electric Corporation. This page is an independent homeowner resource and is not affiliated with, authorized by, or endorsed by Mitsubishi. Brand and code references are used factually for identification and troubleshooting only.
Frequently asked questions
What does the Mitsubishi P5 error code mean?
P5 is a drain pump fault. The unit detected that water isn't being pumped out of the drain pan as it should — usually because the drain line is clogged, the drain pump has failed, or there's a wiring problem to the pump. The system stops to avoid overflowing water inside the indoor unit.
Can I fix a Mitsubishi P5 error myself?
Often, yes — if the cause is a clogged drain. Turn the unit off, clear the condensate drain line (a wet/dry vacuum on the outdoor end works well), and clean any slime out of the drain pan. If the pump stays silent or P5 returns after the line is clear, the pump or its wiring needs a technician.
Why is there water in my unit with a P5 code?
Because the drain pump isn't moving condensate out. As the unit cools it pulls moisture from the air into the drain pan; if the pump can't empty that pan (clog, failure, or wiring), water backs up and the P5 protection stops the system before it overflows.
How do I reset a P5 on a Mitsubishi mini split?
Clear the drain first, then power-cycle: turn the unit off, switch its breaker off for a few minutes, and restore power. Resetting without clearing the blockage just brings P5 straight back, so fix the drain before you reset.
When should I call a professional?
Call a technician if the drain line is clear but P5 keeps coming back, if the drain pump doesn't run or makes no sound, or if you find damaged wiring at the pump. A failed pump usually needs replacing, which isn't a DIY job.