F31 error on an LG dishwasher: A troubleshooting guide

Are you seeing an F31 error on your LG dishwasher? If this message pops up, it usually indicates a problem with the heated air dry fan.

If you need a replacement part, grab your model number and head over to AppliancePartsPros.com to order one. Most orders arrive in two business days.

Let’s walk through the causes behind the F31 error code and the steps for diagnosing and fixing it so you can get your dishwasher working again.

Disclaimer: The troubleshooting information provided in this article is based on general service manuals and may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

What could cause the F31 error code?

The F31 error code typically shows up when the dishwasher’s control board detects an issue with the heated air dry fan motor.

The heated air dry fan is a part of the dishwasher’s drying cycle. It works by blowing hot air onto the dishes to remove excess moisture so your dishes come out dry and sparkling clean. But when the fan motor fails, it can prevent the dishwasher from drying the dishes correctly.

Safety precautions

• Always power off and unplug your appliance or switch off the circuit breaker before attempting any maintenance or replacement work. This keeps you safe by preventing any risk of electric shock.
• Take your time while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Keep your workspace free from clutter and other obstacles. Keep children and pets away while you’re working.
• Never work on internal parts with bare wet hands. Make sure the work area is completely dry.
• Check your user manual to see if there are specific installation or safety instructions for your part or appliance.
• Be gentle when handling or removing parts. Excessive force might damage the appliance, the parts or cause injury.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.

What you need

• Phillips screwdriver
• Flat head screwdriver
• Multimeter with needle probes
• Socket set (various sizes)
• Allen wrench set
• T10/T15/T20 Torx drivers
• Pliers
• Flashlight
• Work gloves
• Cleaning rags

Troubleshooting steps

Step 1 – Check the fan motor

The fan motor helps blow hot air onto the dishes during the drying cycle. Over time, the motor may wear out or fail due to regular use, which can cause the fan to stop working. This can result in an F31 error code.

1. Turn off the dishwasher.
2. Find the fan motor, which is usually located at the back or bottom of the dishwasher.
3. Look over the fan motor for any signs of damage or wear.
4. Check the fan motor mounting bracket to make sure it’s securely attached to the dishwasher.
5. Check for any debris or food particles that may be stuck in the fan blades or the fan motor.
6. Use a multimeter to test the fan motor connections for DC voltage during operation. There should be 12 Volts DC when testing from the blue wire to the gray wire that would be coming from the control. There should be an output signal between 2 to 4.5 Volts DC from the blue wire to the black wire if the fan does rotate. There should also be a signal voltage from the control measuring between 1.5 to 3.5 Volts DC from the blue wire to the light blue wire. If the fan is getting the voltage from the control and not operating, or it does operate but doesn’t send an output signal, then the fan has failed.
7. Replace the fan motor if needed.
8. Reinstall the fan motor and plug the dishwasher back in.

Read more: How To Use A Multimeter To Check Appliance Parts

Step 2 –  Check the thermistor and heater connections

The thermistor is responsible for regulating the temperature of the dishwasher and the heater will heat the air that the fan blows through. If the wire connections are loose, it can prevent the control from working properly.

To check the heater and the thermistor:

1. Remove the bottom panel to access the internal parts.
2. Find the thermistor and the heating element on the fan assembly.
3. Disconnect the wires and plug them back in one at a time to ensure they are secure.

Step 3 – Check the wiring

Issues with the wiring or connections to the fan motor can also cause an F31 error message on your dishwasher. If the wiring is damaged or loose, it can disrupt the flow of power to the fan motor and prevent it from working properly.

1. Turn off the dishwasher and unplug it from the power outlet.
2. Check the wiring and connections to the fan motor and control to see if there are any obvious signs of damage or wear. Replace the harness if you find any signs of damage.
3. Make sure all connections are secure and that there are no loose wires.
4. Use a multimeter to test the wiring for continuity. If there’s no continuity, replace the wiring harness.

Step 4 –  Check and/or replace the control board

In less common cases, the control board itself may be the cause behind the F31 error code. The control board is responsible for sending signals to the fan motor, and if it malfunctions, it can prevent the fan motor from working properly.

1. Try resetting the dishwasher by unplugging it and waiting for 30 minutes before plugging it back in. If the issue persists, you may need to replace the control board.
2. Turn off the dishwasher and unplug it from the power outlet.
3. Find the control board, which is usually located at the top or front of the dishwasher.
4. Look over the control board for any obvious signs of damage or wear. If the board is damaged, replace it with a new one.
5. If the board looks ok, you can check the incoming voltage to the dishwasher. To do this, you’ll need to plug it back in. When testing live voltage, please be extra careful to protect yourself from electric shock, which could potentially cause serious injuries. Never test live voltage if you’re uncomfortable using a multimeter.
6. Reinstall the control board and plug the dishwasher back in. If the error code returns, replace the control board with an OEM part.

Read more: How Does a Dishwasher Work?

Step 5 – Run a test cycle

Once you’ve found out which part caused the F31 error and you’ve made the necessary repairs or replacements, you can turn the dishwasher back on and run a short test cycle.

If the F31 issue persists, repeat the troubleshooting steps above until it’s resolved.

Read more: How to Clean a Dishwasher (with Video!) – AppliancePartsPros Blog

Additional information

Thank you for reading! We hope this guide helped you get your LG dishwasher working again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our thousands of free videos and troubleshooting guides available. If you need replacement parts or some extra help with ordering them, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, read our DIY blog and more.

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