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ErrBase

Mitsubishi Mini-Split E6 Error Code: Communication Fault Between Indoor and Outdoor Units

Quick Answer

Mitsubishi E6 means the communication link between the indoor and outdoor units has failed. These two units exchange data continuously on a 3-conductor communication wire (sometimes called the S1-S2-S3 or control wire). The most common cause is a loose or corroded connection at the terminal block inside the outdoor unit.

Mitsubishi E6 means the communication link between the indoor and outdoor units has failed. These two units exchange data continuously on a 3-conductor communication wire (sometimes called the S1-S2-S3 or control wire). The most common cause is a loose or corroded connection at the terminal block inside the outdoor unit. Check the outdoor unit terminal strip first - corrosion at the screw terminals is very common in coastal or humid climates.

MitsubishiMinisplitSeverity: highDifficulty: intermediate75% DIY Success
Time to Fix
30–120 min
Difficulty
intermediate
Parts Cost
$15 – $350
Tools Needed
Philips screwdriver, Multimeter

What Does the E6 Code Mean?

E6 is the indoor-to-outdoor communication loss code. Inspect the terminal block inside the outdoor unit for loose or corroded connections on the communication wire (typically labeled 1, 2, 3 on the terminal strip). This is the highest-volume Mitsubishi mini-split code.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Loose or corroded connection at outdoor unit terminal block40%
Communication wire damaged by pests or weather24%
Indoor unit PCB failure22%
Outdoor unit PCB (control board) failure14%

Symptoms You May Notice

  • Indoor unit shows E6 on the display
  • Both indoor and outdoor units stop operating
  • Operation lamp blinks
  • System worked fine then stopped suddenly

Can you reset a Mitsubishi minisplit to clear the E6 code?

Turn off the circuit breaker supplying the mini-split for 60 seconds. Turn it back on and power on the unit with the remote control. The E6 code clears from active memory after a power cycle. If the underlying communication fault is fixed, the code will not return.

Tools Required for Diagnosis

Philips screwdriverMultimeterElectrical contact cleaner

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

1

Turn off the circuit breaker supplying the mini-split for 60 seconds

Turn off the circuit breaker supplying the mini-split for 60 seconds. Turn it back on and power on the indoor unit with the remote. Watch for the E6 code to return.

2

Turn off the circuit breaker

3

Trace the communication wire from the outdoor unit back to the

4

If wiring and terminals are confirmed good, check the outdoor unit PCB

5

Restore power and run the unit for 30 minutes

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name
Communication Wire (14-gauge 3-conductor)N/A - use 14 AWG 3-conductor wire · $15–$40
Outdoor Unit PCB (model-specific)T7WE79178 (verify for your model) · $120–$350

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs
Labor Approach
Our Verdict
REPAIR
Estimated Cost: $183 (Parts) vs $1900 (New Machine)

Frequently Asked Questions

What wire connects the indoor and outdoor units on a Mitsubishi mini-split?
A 14-gauge 3-conductor control wire (also called the communication or signal wire) runs between the indoor and outdoor units alongside the refrigerant lines. It is labeled 1, 2, 3 at each terminal block. This is separate from the power wire to the outdoor unit.
Can E6 be caused by a power surge?
Yes. A power surge can damage the communication circuit on either the indoor or outdoor PCB. If the E6 appeared right after a storm or grid event, the PCB on one or both units may have been damaged. Check both boards for burned components.
My Mitsubishi E6 code only appears in winter. Why?
Cold temperatures cause metal terminal blocks to contract, which can loosen screw connections that were already slightly loose. This is very common and explains seasonal E6 patterns. Re-tighten the terminal screws on the outdoor unit in the fall before cold weather arrives.
Can I swap the indoor and outdoor PCBs myself to diagnose E6?
No. PCB replacement on Mitsubishi mini-splits requires the technician to configure the replacement board to match the unit using a setup procedure. Incorrect configuration can cause further faults. Have a certified Mitsubishi Diamond Contractor handle board replacements.
How long does communication wire last on a mini-split?
The communication wire can last the full life of the system (15 or more years) if properly routed and protected. Wire failures are almost always due to physical damage (pest chewing, improper routing, or UV degradation on unprotected outdoor sections) rather than normal aging.

Related Mitsubishi Minisplit Error Codes

Code: HUBMitsubishi Mini-Split Error Codes: Complete MSZ and MXZ Series GuideCode: RESETMitsubishi Mini-Split Error Codes: Complete MSZ and MXZ Series Guide

Same Fix on Other Brands

Daikin E7: LG CH10:

Models Known to Experience E6 Errors

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

MSZ-GL12NA, MSZ-FH12NA, MSZ-FS12NA, MXZ-2C20NAHZ

Last verified for technical accuracy on March 14, 2026