- HVAC
- Smoke and CO alarms
ERR
Kidde ERR on digital CO alarm: end of life or sensor malfunction
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On a Kidde CO alarm with a display, ERR points to end of life, a power surge or a sensor error. While it shows, the unit does not detect carbon monoxide properly: try the 5 second reset and replace the alarm if ERR returns.
Safety first
Stop and check this first
- Kidde says that whenever a digital unit shows a number, with or without an alert, you should assume it senses CO: leave the home and call 112 or your local emergency number (911 in the US).
- An end of life ERR is not cured by resets or fresh batteries: replace the alarm, because Kidde warns it will not detect CO in that state.
Safe checks you can perform
- Read the back label and the date of manufacture
- Hold Test/Reset for 5 seconds and wait
- Read the code with Peak Level and call Kidde
Leave these tasks to a qualified professional
- Do not attempt this professional task: Kidde support case and warranty decision
- Do not attempt this professional task: Replacement by an electrician for hardwired alarms
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Kidde support case and warranty decision
What they doKidde customer support takes the E code, model and date of manufacture and decides whether to send a replacement alarm.
They must show youwhat the E code read with Peak Level means on your model.
In writingthe case number, the error code, the date of manufacture and the warranty decision.
Replacement by an electrician for hardwired alarms
What they doIf your CO alarm is wired to the mains, a qualified electrician removes the old unit and connects the new one.
They must show youthe mains voltage and interconnect wiring checked after the new alarm is fitted.
In writingthe date of manufacture of the new alarm and confirmation that it passed a test with the test button.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Read the back label and the date of manufacture
- Who:
- you, with the alarm in hand or in place, without opening it.
- How:
- find the model number, date of manufacture and assembly number (if visible) on the back; Kidde asks you to have these ready when calling support.
- Result that matters:
- knowing whether the unit has already reached the 7 or 10 year life Kidde mentions.
- If it is past its service life:
- do not try to extend it, buy a new alarm and fit it as soon as you can.
- If it is newer:
- move on to the 5 second reset Kidde describes.
- Evidence to keep:
- a photo of the back label showing model and date.
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
Hold Test/Reset for 5 seconds and wait
- Who:
- you, following the Kidde procedure.
- How:
- press and hold Test/Reset for 5 seconds, then release; if the display returns to zero, keep an eye on the alarm for the next few minutes.
- Result that matters:
- telling a one-off power surge apart from a real malfunction, which Kidde says brings ERR back within 5 minutes.
- If the display stays at zero:
- it was most likely a surge; run a normal test with the test button.
- If ERR comes back within 5 minutes:
- it is a real malfunction; go on to read the error code.
- Evidence to keep:
- the time of the reset and what the display showed afterwards.
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
Read the code with Peak Level and call Kidde
- Who:
- you, with the alarm within reach.
- How:
- press and hold Peak Level: the ERR message turns into a code made of an E and two digits; note it down and call Kidde product support with the model, date of manufacture and assembly number.
- Result that matters:
- letting support decide whether it is a non-recoverable fault and whether a warranty replacement applies.
- If it is still inside the warranty period:
- Kidde says a replacement will be mailed to you.
- If the warranty has run out:
- replace it with a new alarm, because it will not detect CO in this state.
- Evidence to keep:
- the E code written down, a photo of the display and the case number.
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- HVAC
- Brand
- Kidde
- Product type
- Smoke and CO alarms
Known code variants
- Kidde CO alarm display ERR
- Kidde CO alarm ERR end of life
- Kidde CO pantalla ERR código E03
- Kidde detector digital CO muestra ERR
- Kidde detector monóxido pantalla Err
- Kidde digital CO detector Err message
- Kidde ERR carbon monoxide alarm
- Kidde ERR code E03 peak level
- Kidde ERR detector de CO
- Kidde Err fin de vida detector CO
What it means
On the Kidde page about the ERR message on its digital CO alarms, ERR appears once the alarm reaches its 7 or 10 year life, after a power surge, or when there is a sensor error, which is confirmed if pressing Peak Level shows a code such as E03. Kidde warns that the alarm will not function correctly while an error code is present, and that end of life and malfunctions that will not reset are non-recoverable: the unit must be replaced. Other models may differ; the message alone does not prove which part has failed, but your home may be left without CO protection.
Warnings and stop conditions
- Highsource verified
Kidde says that whenever a digital unit shows a number, with or without an alert, you should assume it senses CO: leave the home and call 112 or your local emergency number (911 in the US).
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
- Highsource verified
An end of life ERR is not cured by resets or fresh batteries: replace the alarm, because Kidde warns it will not detect CO in that state.
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
Symptoms and causes
Probable causes · in order
- The alarm has reached end of lifeCommon
Kidde says ERR appears once the alarm has been active for its 7 or 10 year life, and that it no longer detects carbon monoxide in that state.
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
- A power surgePossible
When a surge is to blame, Kidde explains that holding Test/Reset for 5 seconds sets the display back to zero and the zero stays there.
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
- Sensor error or internal malfunctionPossible
If pressing Peak Level brings up a code starting with E, such as E03, Kidde treats it as a sensor error; if it will not reset, the alarm has to be replaced.
Evidence: What Does an ERR Message Mean on My Carbon Monoxide Alarm?
Virtual technician
Does ERR still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Why Is My Carbon Monoxide Alarm Beeping or Chirping?
Kidde · 2026 · official_doc
- 2
What Does an ERR Message Mean on My Carbon Monoxide Alarm?
Kidde · 2026 · official_doc
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