CH05 - Communication between the indoor and outdoor units is unstable or interrupted.
LG says CH05, E0, and CH53 can appear when an inverter air conditioner has a communication error between the indoor and outdoor units. Shortly after installation or relocation, that can point to installation-related communication issues. During normal use, LG says it can also be a temporary electrical or power-instability fault.
Based on LG USA support articles for wall-mounted and related inverter split air conditioners; exact indicators and alternate code labels can vary by model.
Severity
High
Display
On applicable wall-mounted models, the code may appear as CH05 on the display or be represented by the indoor-unit indicator blinking pattern described by LG for wall-mounted air conditioners.
Support first?
Often not
Models in range
Wall-mounted inverter split air conditioners, 2-in-1 heating and cooling air conditioners
What to do first
Start with these checks
- 1Turn the unit off at the breaker or unplug it, wait about 5 minutes, and restore power once.
- 2If the error started right after installation or relocation, stop troubleshooting and contact the installer.
- 3Avoid repeated resets if the code returns immediately.
Likely causes
What usually sits behind this code
Indoor and outdoor units are not communicating correctly.
Temporary unstable power supply or other electrical issues.
Installation or relocation introduced a wiring or connection problem.
Contact support
Contact customer support if any of these apply
- !CH05 comes back after one power cycle.
- !The error began after installation or relocation.
- !You suspect wiring, breaker, or unit-to-unit communication problems.
- - LG notes some models may show EO while the kW Manager is operating.
- - LG says wall-mounted units can indicate faults through LED blink patterns rather than a full text display.
Related codes
Nearby codes in this family
More ranges
More LG air-conditioner ranges
Source notes
Source and scope
Source: LG USA Support
LG identifies CH05, E0, and CH53 as indoor-to-outdoor communication errors and recommends a 5-minute power reset, with service if the error persists.
Last reviewed: 2026-04-19
Use only simple checks that LG explicitly recommends. Do not open panels or attempt wiring repairs yourself.