Understanding carbon monoxide alarm error codes is crucial to keeping you and your loved ones safe, especially since an alarm won’t function correctly while an error code is present. Here’s why your Kidde carbon monoxide alarm may be displaying an ERR message:

  • End-of-life- ERR will appear once the alarm has been active for its 7- or 10-year life to signal an end-of-life warning.
  • Power Surge- If you think a power surge is the cause of the ERR message, press and hold the Test/Reset button for 5 seconds. The reset should change the display to zero and stay there if that is the case.
  • Alarm Malfunction- ERR will also appear if there's a sensor error. If you press the peak level button and a code appears (for example, E03), this is the case.

Alarm malfunctions that won’t reset and end-of-life warnings are "non-recoverable" errors, and the alarm must be replaced since it will not detect carbon monoxide in these states. If the unit is within warranty, please call customer support at 1-800-880-6788 to request a replacement.

What to Do When an ERR Message Appears on a Carbon Monoxide Alarms Digital Display

The first step to understanding whether your carbon monoxide alarm needs to be replaced is to identify the meaning behind the error code displayed.

In the rare event that your alarm malfunctions, it will alert you with a short chirp and an amber LED flashes every second and a green LED flashes error code every other 30 second period. Here’s what you’ll need to do:

  • Push and hold the Test/Reset button for 5 seconds, and then release the button. If the reset is successful, the display will reset to zero. If it's an actual malfunction, the unit will go back to Err within 5 minutes.
  • If it does turn out that your alarm is malfunctioning after you reset it, you need to press and hold down the Peak Level button. The ERR message will change to an ERR code, which will start with an E and have two numbers behind it.
  • Once the error code is displayed, call us on our hotline at 1-800-880-6788, provide an agent with the code, and they will assist you further. Please make sure that you have your alarm's model number, date of manufacture, and assembly number (if visible), so you will not have to call back.

How to Retrieve the Error Code on a Carbon Monoxide Alarm

Push and hold the Peak Level button. You will see an E and an O followed by a number.

Contact product support at 1-800-880-6788 and provide us the error code, along with the model number, assembly number, and date of manufacture from the back of your unit.

Additional Carbon Monoxide Display Codes

There are also other codes that you may see displayed on your carbon monoxide alarm. Here are some scenarios you need to be aware of:

What Does it Mean When 200 Appears on Your Carbon Monoxide Alarms Display?

Any time you push the Test/Reset button, the unit will go through a series of numbers that are programmed to test the unit's internal diagnostics.

This will start out with an 888 reading, then display numbers usually in the 200 ranges, then back to 888, and back to zero. They are not actual readings, so you should not be alarmed and do not need to take any further action.

What Does it Mean When Your Carbon Monoxide Alarm Displays a Number with No Alarm?

Any time a digital unit displays a number with or without an alert, you should assume it senses carbon monoxide. Leave the home and call 911.

Digital Display of a Carbon Monoxide Alarm Showing "Lb"

"Lb" is the signal for a low battery. The capital L with a lower-case b on your digital display is letting you know the battery is low and needs to be replaced.