Error code reference

LG Heat Pump Error Code 51

Indoor connection over capacity: total connected indoor unit capacity exceeds outdoor unit rated capacity (130% for 10HP, 115% for 4.5HP, 120% for 6HP).

SourceLG Heat Pump Air Conditioner - Service Manual: CRUN/CRNN Seriesp. 244

LG codes LG heat pump codes

Diagnostic procedure

The full 51 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

Verify if total indoor unit capacity is within limits; if yes, confirm indoor unit capacity code and replace PCB.

SourceLG Heat Pump Air Conditioner - Service Manual: CRUN/CRNN Seriesp. 244

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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

2 manuals in the MyPros+ library document this code for LG heat pump.

Models covered by the manuals that document this code

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The full 51 procedure

Where this code is documented

Models covered by the manuals that document this code

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