F21 error on a Frigidaire electric wall oven: How to troubleshoot

Is your electric wall oven showing that pesky F21 error code? No worries! We’ve got just what you need to figure out why it’s displaying and how you can fix it.

The F21 error usually means there’s a problem in communication between the oven’s main electronic control board and the auxiliary convection board.

If you find out that you need any replacement parts for your electric Frigidaire wall oven, you can enter your model number at AppliancePartsPros.com to order them. Most orders arrive in just two business days, and we have thousands of free guides to show you how to install your new parts.

Let’s dive in and get your oven baking 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.

READ MORE: A Simple Guide to Oven Hot Spots

Reasons behind the F21 error code

First things first – let’s get a grasp on what the F21 error code means.

All electric wall ovens have two main electronic circuit boards: the primary control board and a secondary auxiliary board. To make sure everything runs smoothly, these two boards need to communicate. When the controller senses a communication breakdown from the auxiliary board, it will flash the F21 diagnostic code on the display.

The F21 error usually means the main control can’t send or receive signals to/from the auxiliary convection circuit board. This can mess up the oven’s bake and roast modes.

READ MORE: Guide to oven rack placement for baking & roasting

Keep safety first

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind:

• Always power off and unplug your appliance or switch off the circuit breaker before you attempt any maintenance or replacement work. This keeps you safe by preventing any risk of electric shock.
• If the appliance has recently been used, give it plenty of time to cool down before working on it.
• Take your time while working to prevent accidents and personal injuries. Rushing is the enemy of precision.
• Work in a well-lit area so you can clearly see and access appliance parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with wet hands. Make sure the work area is completely dry.
• Check the user manual to see if there are specific installation or safety instructions related to your appliance or replacement part.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause personal injury.
• Wear insulated work gloves to protect your hands from sharp metal parts and debris.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Don’t test live voltage with a multimeter if you’re unfamiliar with how to prevent short-circuiting.
• Consider wearing safety glasses and/or a dust mask when working with chemicals, dust or a large amount of debris to prevent irritation or injury.

READ MORE: Don’t Get Burned! 14 Quick and Easy Oven Safety Tips

Troubleshooting steps

Step 1 – Check the wire harness

1. Look over all the wiring connecting the two circuit boards. Carefully examine the harness plugs at connector locations P1 on the auxiliary board and P4/P10 on the primary controller. Look for signs of wire damage like cuts, abrasions, cracks, or exposed copper strands.
2. Gently pull on each wire to check for loose or corroded terminals.
3. Use a multimeter to check the wiring for continuity by setting it to the continuity setting (the symbol looks like a sideways WiFi symbol) and placing the meter leads on each end of the wire. If there’s continuity, then the wire harness is good. If it doesn’t, then you’ll need to replace the harness.

READ MORE: 6 Cleaning Tips to Keep Your Appliances In Top Shape Over Time

Step 2 – Check the auxiliary board

If reseating the connections doesn’t solve the problem, the auxiliary board may need to be replaced.

1. Make sure the oven is turned off and unplugged.
2. Gain access to the back of the oven.
3. Find and remove the two retaining screws holding the auxiliary board in place.
4. Carefully lift the board out and check it for signs of water damage or burns.
5. If the board checks out OK, use a multimeter to test for voltage coming from the main control board to the auxiliary board. You’ll need the oven’s power on for this test, so please take extreme caution to prevent electric shock, which has the potential to cause serious injuries. Never test live voltage if you’re not comfortable using a multimeter. Be sure to check your tech sheet for testing locations and the acceptable readings for your specific unit.

You’ll need to replace the board if there’s power going to it and it’s not sending power out.

READ MORE: Your Guide to Cooking Without an Oven

More information

Thank you for reading! We hope this guide helped you get your Frigidaire electric wall oven working again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our other troubleshooting guides and videos.

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. We can also help you troubleshoot common oven problems here.

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