Error code reference

LG Air Conditioner Error Code 40

Master outside unit inverter compressor CT sensor error - MICOM input voltage not within 2.5V ±0.3V at initial state of power supply.

SourceLG Air Conditioner Outside Unit - Service Manual: ARNU/URNU Seriesp. 107

LG codes LG air conditioner codes

Diagnostic procedure

The full 40 procedure

Step 1 is visible so you can confirm you are on the right page. The remaining steps, the ones that tell you whether to actually replace a part, unlock with any pass.

MyPros+ · DiagnosticsStep 1 preview

First diagnostic step

Check if input voltage is normal (R-S/S-T/T-R phase voltage 220V ±10%).

SourceLG Air Conditioner Outside Unit - Service Manual: ARNU/URNU Seriesp. 107

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More steps, wiring diagram references, and verified part numbers

Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.

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Where this code is documented

70 manuals in the MyPros+ library document this code for LG air conditioner.

Models covered by the manuals that document this code

More models are covered than are listed here.

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The full 40 procedure

Where this code is documented

Models covered by the manuals that document this code

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