LG Washer Error Code AC4

The AC4 code indicates a communication error between the LCD Module (control panel display) and the main PBA (main control board). The washer is not detecting the expected signals between these two components. This is usually caused by a loose connector, a poorly seated wiring harness, or a faulty solder joint on one of the boards.

A reset may temporarily clear the AC4 code, but if the underlying connection problem is not fixed, the error will return. Unplugging the washer for a few minutes and restarting it can be used to confirm whether the fault is intermittent, but a proper repair of the connector or solder joint is necessary for a permanent fix.

If the fix is simply reseating a loose connector, there may be no parts cost at all, though a service call can run anywhere from $75 to $150 for labor. If the LCD Module needs replacement, parts and labor typically range from $100 to $250 depending on the model. A main PBA replacement is generally the most expensive repair, often ranging from $150 to $350 or more for parts and labor.

Start by unplugging the washer, then locate and inspect the connector between the LCD Module and the main PBA. Unplug and firmly reseat the connector on both ends to ensure a solid connection. If the error returns after that, the solder joints on each board should be inspected, and if no physical fault is found, one or both components may need to be replaced.

It is not recommended to continue running the washer while the AC4 error is active. A communication failure between the control panel and the main board means the machine may not properly execute or complete cycles. Running the washer in this state could lead to incomplete wash cycles or unexpected behavior.