Mitsubishi Mini-Split Error Codes: MSZ and MXZ Guide

Quick Answer

Mitsubishi mini-split error codes like E6 or P4 indicate specific component faults or maintenance needs. The most common fix is resetting the system at the breaker for 5 minutes to clear transient faults and checking for clogged drain lines.

Mitsubishi systems are honestly some of the most reliable mini-splits I work on, but they're really sensitive to communication and drainage issues. Ignore an error code long enough and you're looking at a flooded ceiling or a burned compressor. Most of what I see in the field is either a clogged drain line throwing a P4 or a loose wire at the S3 terminal causing an E6. Neither one's that hard to fix if you know where to look.

MitsubishiMinisplit

About These Mitsubishi Minisplit Error Codes

OK so here's the deal. Mitsubishi splits these faults into two categories and once you know which bucket you're in, you've already done half the work. E-codes mean the indoor and outdoor boards stopped talking to each other. P-codes mean a sensor caught something it didn't like, water backing up, a coil freezing over, a compressor running hot. These units are actually pretty good at telling you exactly what's wrong if you know how to read them.

Most Common Error Codes

Indoor to outdoor unit communication loss (E6)40%

Drain pump failure (E9)24%

CT sensor fault (P6)14%

Drain float switch activated (P5)12%

Drain pan overflow (P4)10%

Symptoms You May Notice

Operation light is flashing in a repeating pattern instead of glowing steady, and the unit won't respond to any button on the remote.
System runs for 10 or 15 minutes then shuts itself off completely, and when you check the display there's a code blinking that wasn't there before.
You can hear the outdoor unit spinning but the indoor unit is just pushing room-temperature air, no heating or cooling happening at all.
Water is dripping from the bottom of the indoor unit or you see staining on the wall below it.
Unit is completely dead, no lights, no display, nothing, because the condensate float switch killed all power to protect your home from water damage.

Tools Required for Diagnosis

Phillips #2 screwdriverFlathead screwdriverFlashlightShop vacuum with hose attachmentMultimeterCompressed air canWet rags or towelsZip ties

How to Identify Your Error Code

Frequently Asked Questions

How do I retrieve a Mitsubishi mini-split error code from the remote?

If your indoor unit's just blinking and not showing a code, you can force it to tell you what's wrong. Point the remote at the unit and press the Mode button ten times within five seconds. The unit'll enter a service mode and the display will cycle through stored codes. Listen for a long beep, that's the active fault that triggered the shutdown. Write it down before you do anything else, because cycling the breaker can wipe it from memory and you'll be starting from scratch.

What do E-codes versus P-codes mean on Mitsubishi mini-splits?

Think of E-codes as communication errors. The indoor and outdoor units have stopped talking to each other, basically a severed connection somewhere in the wiring. P-codes are protection trips. The sensors are working perfectly but they've detected something dangerous like an overflowing drain pan or a compressor that's overheating. Here's why that distinction matters: P-codes are usually something you can handle yourself because they typically involve cleaning something. E-codes are trickier because they usually mean tracking down a damaged wire or replacing a control board.

My Mitsubishi mini-split shows an error but the remote doesn't display a code. What do I do?

When the remote stays blank, you've got to watch the Operation and Timer lights on the indoor unit. They blink in a specific repeating pattern. Two blinks followed by a pause, for example, usually points to the room temperature thermistor. Count the blinks carefully and look up the sequence in the code-specific guide for your model. If you can't sort it out from the blink count alone, the Mode button trick will usually force the code onto the screen so you don't have to keep counting and second-guessing yourself.

How often should I service my Mitsubishi mini-split to avoid error codes?

Wash the indoor filters every month, especially if you've got pets or live somewhere dusty. I tell every customer this and honestly maybe half of them actually do it. Once a year, get a tech out to check the outdoor coil. If it gets packed with cottonwood or dirt, the system pressure spikes and you'll end up with protection codes that can eventually kill the compressor. A $150 annual tune-up is way cheaper than a $2,000 compressor replacement, so just make the appointment.

Can I fix a Mitsubishi mini-split error code myself, or do I need to call a pro?

Depends completely on the code. P4, P5, P8? Yeah, most homeowners can handle those. You're clearing a drain line or cleaning a filter. E6 where you found a chewed wire? Also manageable if you're comfortable with basic electrical work. But inverter board faults, confirmed refrigerant leaks, or compressor issues? That's pro territory. You need an EPA 608 certification to legally handle refrigerant anyway, so anything involving the refrigerant circuit isn't a DIY job no matter how handy you are.

Related Mitsubishi Minisplit Error Codes

Code: E6Mitsubishi Mini-Split E6 Error Code: Communication Fault Between Indoor and Outdoor Units Code: E9Mitsubishi Mini-Split E9 Error Code: Drain Pump Malfunction Code: P6Mitsubishi Mini-Split P6 Error Code: Current Transformer Sensor Fault Code: P4Mitsubishi Mini-Split P4 Error Code: Drain Pan Overflow Code: P5Mitsubishi Mini-Split P5 Error Code: Drain System Malfunction Code: P8Mitsubishi Mini-Split P8 Error Code: Freeze Protection or Low Refrigerant

Models Known to Experience HUB Errors

This repair applies to most Mitsubishi minisplits with this error code. Common model numbers include:

MSZ-GL09NA, MSZ-GL12NA, MSZ-GL18NA, MSZ-FH12NA, MSZ-FS12NA, MSZ-EF12NA, MXZ-2C20NAHZ, MXZ-3C24NAHZ

Written by

Raj Patel

HVAC & Water Systems Specialist · 15 years experience

Last verified for technical accuracy on March 14, 2026