This Knowledge Base article (KB) explains the meaning of  log message, " chas[694]: cm_read_i2c errno:5, device:19 ", and why this message is logged.

When a 190W DC power supply is used with the EX Series Switches, the POE (Power over Ethernet) controller cannot be used.

POE is not supported with the use of the 190W DC Power supply by design.

As a result when the EX Switch detects a DC power supply being used, it will turn off the POE controller. The log message chas[694]: cm_read_i2c errno:5, device:19 is seen in this case.

This log message indicates that POE device id 19 is being turned off. Currently this message is displayed continuously on the EX Switch.  A Juniper Problem Report (PR) has been opened to suppress this message so that it is not continuously logged. The Juniper Problem Report (PR) number associated with this is PR 437579 . With the JUNOS EX Switch software releases that contain the fix to PR 437579 , the message will no longer be displayed.

If you are continuously seeing this message, it indicates that POE controller is being disabled due to the use of the DC power supply. Please contact Juniper Technical Assistance Center (JTAC) for any further inquiries regarding the release which contains fix to PR 437579 in order to suppress this message.