Error code reference

LG Air Conditioner Error Code 151

Outdoor 4-way (reversing valve) switching error; pressure change does not occur when Main or Sub outdoor has a 4-way valve error.

SourceLG Air Conditioner - Full Service Manual: LRUV/LRUN/LRNU Series (R22)p. 170, 237

Diagnostic procedure

The full 151 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
1
First diagnostic step
Check whether the piping between the outdoor units is normal (liquid pipe to liquid pipe, common pipe to common pipe).

SourceLG Air Conditioner - Full Service Manual: LRUV/LRUN/LRNU Series (R22)p. 170, 237

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

34 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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