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System fault and error codes on a CPAP machine

A fault message means the machine has found a problem with itself. Some faults stop the air; one (ResMed’s Error 4) has causes you can fix. What each maker says to try, and when each says to stop and contact your provider. None of them wants you to open the machine.

Therapy settings: This page explains what a CPAP machine’s screen or light is telling you, in the maker’s words. It is not medical advice: ask your equipment provider or clinician about your therapy settings, and do not change your pressure or any prescribed setting because of anything here.

ResMed

  1. ResMed AirSense 11 Words on the screen

    System fault, refer to user guide, Error 4

    ResMed gives three possible causes: the machine may have been left somewhere hot; the air filter may be blocked; there may be water in the air tubing.

    What ResMed says to do

    1. If it was somewhere hot, allow it to cool before use.
    2. Check the air filter and replace it if it is blocked.
    3. Empty any water from the air tubing.
    4. Then disconnect the AC adaptor and reconnect it to restart the machine.

    Source: AirSense 11 user guide (Americas) (ResMed, 398133/2, 2021-10), checked 2026-09-29.

  2. ResMed AirSense 11 Words on the screen

    Any other “System fault, refer to user guide Error X”

    An unrecoverable error has occurred on the machine.

    What ResMed says to do

    1. Contact your care provider. Do not open the device.

    Source: AirSense 11 user guide (Americas) (ResMed, 398133/2, 2021-10), checked 2026-09-29.

  3. ResMed AirSense 10 Words on the screen

    System fault, refer to user guide, Error 0XX (and all other error messages)

    An unrecoverable error has occurred on the machine.

    What ResMed says to do

    1. Contact your care provider. Do not open the device.

    Source: AirSense 10 user guide (AirSense 10 AutoSet, AutoSet for Her, Elite and CPAP, with HumidAir) (ResMed, 378947/1, 2021-02), checked 2026-09-29.

Everything else ResMed’s machines show: ResMed CPAP icons and messages.

Philips Respironics

Everything else Philips Respironics’s machines show: Philips Respironics CPAP icons and messages.

Fisher & Paykel Healthcare

  1. Fisher & Paykel Healthcare SleepStyle Words on the screen

    Error code 100–199

    The machine may not be able to provide effective therapy: it may have shut down, or may not be able to provide your prescribed pressure.

    What Fisher & Paykel Healthcare says to do

    1. Turn the power off and on at the power supply to restart the device.
    2. If the error persists or comes back, consult your healthcare provider. Do not try to repair the device yourself.

    Source: F&P SleepStyle Use and Care Guide (SleepStyle Auto, SleepStyle CPAP) (Fisher & Paykel Healthcare, Use and Care Guide, English section A), checked 2026-09-29.

Everything else Fisher & Paykel Healthcare’s machines show: Fisher & Paykel Healthcare CPAP icons and messages.

React Health

  1. React Health Luna G3 Words on the screen

    Device Fault!!!

    An audible alert: no airflow is coming out of the machine. The screen shows “Device Fault!!!”.

    The alert table gives no step. React Health’s troubleshooting table says to unplug the power cord and plug it back in 20 seconds later when the screen shows nothing or the machine will not start, and to contact your home care provider when no cause can be found.

    Source: Luna G3 APAP / Luna G3 CPAP User Manual (React Health, V1.7, issue date February 29, 2024), checked 2026-09-29.

Everything else React Health’s machines show: React Health CPAP icons and messages.

Other things a CPAP machine shows

Sources

Each maker’s own user guide only, read on the date shown. Nothing here comes from third-party CPAP forums or “error code” sites.

Find any icon, message or light on your machine →