Error code reference

LG Dishwasher Error Code F-9

Low voltage (below 90 volts) detected; dryer will operate and fault code is not displayed unless checked…

LG codesLG dishwasher codes

Low voltage (below 90 volts) detected; dryer will operate and fault code is not displayed unless checked manually.

First step from the service manual

Press OFF pad and while holding OFF pad, press PAUSE/RESUME pad and hold for 2 seconds to display; check electrical circuit that dryer is on.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What F-9 means on a LG dishwasher

The F-9 code on an LG dishwasher indicates the control board has detected supply voltage dropping below 90 volts AC. This is a passive fault, meaning the unit will continue to operate and the code will not appear on the display automatically. Technicians must manually call up the fault by pressing and holding the OFF pad, then pressing and holding the PAUSE/RESUME pad for two seconds. The fault points to the incoming electrical circuit supplying the dishwasher, not the appliance's internal components.

For homeowners, this means the dishwasher is not receiving enough voltage from the wall circuit to operate reliably. Standard household appliances require 120 volts AC, and anything below 90 volts is considered critically low. The dishwasher may appear to run, but under-voltage conditions can cause motors and heating elements to work harder than designed, shortening their lifespan and producing poor wash results.

The most common sources of this problem are a weak or failing electrical circuit, a faulty outlet, a deteriorated power cord connection, or a broader utility supply issue affecting the home. Because this fault is hidden unless manually retrieved, many owners experience repeated performance problems without ever knowing a voltage issue is present.

Source: manufacturer service documentation.

Common causes of F-9

  1. 01

    Under-voltage from the home electrical supply

    Wiring / connection

    If the utility supply to the home is running low or the service panel has a weakened leg, the dishwasher's circuit may consistently measure below 90 volts. This affects the entire branch circuit, not just the appliance.

  2. 02

    Overloaded or shared circuit causing voltage sag

    Wiring / connection

    When the dishwasher shares a circuit with other high-draw appliances, voltage can sag below the 90-volt threshold during operation. Running the dishwasher on a dedicated 20-amp circuit is the correct configuration.

  3. 03

    Loose or corroded wiring at the outlet, junction box, or terminal block

    Wiring / connection

    A loose neutral or hot connection anywhere between the panel and the dishwasher's terminal block creates resistance that drops voltage under load. Inspect the outlet, any junction points, and the dishwasher's internal wire connections at the terminal block.

  4. 04

    Failing wall outlet or damaged power cord

    Part replacement

    A degraded outlet with worn contacts or a power cord with internal wire damage can create enough resistance to drop supply voltage below 90 volts when current is drawn. Replacing the outlet or power cord resolves this.

See the test procedure for each cause

Frequently asked questions about F-9

What does F-9 mean on an LG dishwasher?
F-9 means the dishwasher's control board has detected incoming supply voltage below 90 volts AC. This is a low voltage fault specific to the electrical circuit the dishwasher is connected to. Unlike most error codes, F-9 does not appear on the display automatically and must be retrieved manually by pressing and holding the OFF pad, then pressing and holding PAUSE/RESUME for two seconds.
How do I display the F-9 error code on my LG dishwasher?
Press and hold the OFF pad, then while keeping it held, press and hold the PAUSE/RESUME pad for two seconds. The control board will display any stored fault codes, including F-9. The code is stored in memory even though it does not show during normal operation.
Can I still use my LG dishwasher if it has an F-9 code?
The dishwasher will continue to run with this fault active, but operating consistently below 90 volts is not safe for the appliance long-term. Low voltage forces motors and heating elements to draw higher current to compensate, which generates excess heat and accelerates wear. You should address the electrical supply issue before continuing regular use.
How much does it cost to fix an F-9 error on an LG dishwasher?
If the problem is a loose wire connection at the outlet or junction box, the fix costs nothing beyond your time. Replacing a standard wall outlet runs $5 to $20 in parts. If the circuit is overloaded and needs to be dedicated or upgraded, an electrician typically charges $150 to $300 for that work. If low utility voltage is the cause, contact your power company, as correction is their responsibility and typically no cost to you.
Why does my LG dishwasher have an F-9 code but still seems to work fine?
F-9 is a hidden fault that does not interrupt operation or trigger a visible alert during normal use. The dishwasher stores the code internally and continues running, which is why you may not notice any immediate problem. Over time, sustained low voltage causes poor cleaning performance, longer cycle times, and premature motor failure, so the absence of obvious symptoms does not mean the condition is harmless.

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