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Mitsubishi Electric Air Conditioner P4 / P5 Error Code

Drain sensor or drain pump problem. What it means, which models show it, and how to clear it, easiest fix first.

Mitsubishi ElectricAll Mitsubishi Electric air conditioner codes

P4 / P5
Moderate DIY

The indoor unit has found a problem with its condensate drain system. P4 points to the drain sensor or float switch, and P5 to the drain pump or a drain overflow. A clogged drain line, a stuck float or a failed pump is the usual cause.

Compatible models

Mitsubishi Electric doesn't publish a model list for this code; it appears on Mitsubishi Electric air conditioners with a digital display. Check your owner's manual.

Also shown as

These check codes appear on wired wall controllers, mainly with P-series, Mr. Slim and ducted or ceiling units; wall-mounted M-series units (MSZ) usually report faults by blinking the OPERATION light instead. The meanings here come from Mitsubishi Electric's Mr. Slim code list for Singapore models and its North American wired-controller manual, and they can differ by series and region, so check your manual. These codes mainly appear on ceiling cassette and ducted units with a built-in drain pump.

Difficulty

Start with the safe checks below; a worn part may need replacing.

Safety first: unplug the air conditioner (or switch off its breaker) before touching filters, hoses or panels. If you smell burning or gas, or see water near the outlet, stop and call a professional.

How to fix Mitsubishi Electric P4 / P5

  1. Switch off the power

    Switch off the system at the breaker. If water is dripping near an outlet or light, switch off that circuit too and don't touch wet fittings.

  2. Clear the drain line outlet

    Find where the condensate line ends, outdoors or at a floor drain, and clear any dirt, algae or debris you can reach at the open end.

  3. Clean the filters and reset

    Wash the indoor filters, let them dry and refit them, then restore power and restart the unit.

When to call a technician

If the code returns, have a technician check the drain pump, float switch and internal drain pan.

Parts linked to P4 / P5

These are the parts most often behind this code. Tap one to see what it does and the signs it is failing.

Order parts by your full model number so they fit.

Frequently asked questions

What does P4 / P5 mean on a Mitsubishi Electric air conditioner?

The indoor unit has found a problem with its condensate drain system. P4 points to the drain sensor or float switch, and P5 to the drain pump or a drain overflow. A clogged drain line, a stuck float or a failed pump is the usual cause.

Which Mitsubishi Electric models show the P4 / P5 code?

Mitsubishi Electric doesn't publish a model list for this code; it appears on Mitsubishi Electric air conditioners with a digital display. Check your owner's manual.

Can I fix Mitsubishi Electric P4 / P5 myself?

Often. The first steps above are safe checks a homeowner can do. If they don't clear P4 / P5, the cause is likely a worn part that needs replacing.

What if P4 / P5 keeps coming back?

A code that returns after a reset and the checks above usually means a part is wearing out. Note when P4 / P5 appears (which cycle, how often) and have your model number ready; it helps a technician bring the right part on the first visit.

Other Mitsubishi Electric air conditioner codes

Last reviewed 2026-10-19. Codes and steps can vary by model; check your owner's manual.

Sources we checked