This message usually means that you need to replace the specified fan.
The CHASSISD_FAN_FAILURE message is logged each time a fan failure is detected. The chassisd process will raise an alarm and increase the speed of the remaining fans to full speed.
The alarm you will see should look similar to this:
CHASSISD_FAN_FAILURE: SRX220 Chassis fan 0 in slot 0 failed
This message generally only appears when a fan has failed and needs to be replaced.
Verify with following commands:
show chassis alarms
show chassis environment
show chassis hardware
Occasionally, you will see these messages when some other component, upon which the fans depend, fails. This can be a control board or even the chassis.
J-series routers are sometimes subject to false fan-failure messages that are due to intermittent power fluctuations. They will raise an alarm for five seconds, then clear again. These do not have any service impact and are safe to ignore.
If you see these messages, note the platform you are on. Check the device to verify that the fans specified are actually not working. If you are on a J-series router, check the logs to see if the alarms are clearing every five seconds.
If your device has multiple fan trays and all of them begin to throw this alarm at the same time, then this probably indicates a failure of a control board, rather than the fans.
Additionally, if you replace a fan and continue to get this alarm, this is an indication of a problem in a component other than the fan. If you are able, try the fan in a different chassis to verify if has failed. If the fan works in a different chassis, then you know that some other component is causing the alarm.
Generally, the solution is to replace the fan that throws this alarm.