The following messages might be seen if T3 interface is unused and not connected.

Jul  5 19:45:52  HKGCW-PR2 fpc3 DS3(3/1): %PFE-3: main card BT crc error
Jul 22 07:23:49  HKGCW-PR2 fpc1 DS3(1/1): %PFE-3: main card BT crc error
Jul 23 11:11:37  HKGCW-PR2 fpc1 DS3(1/1): %PFE-3: main card BT crc error
Jun 24 22:33:05  HKGCW-PR2 fpc1 DS3(1/1): %PFE-3: BERT irq handler called(0)
Jun 26 15:39:34  HKGCW-PR2 fpc1 DS3(1/1): %PFE-3: BERT irq handler called(0)
Jun 28 00:02:12  HKGCW-PR2 fpc1 DS3(1/1): %PFE-3: BERT irq handler called(0)

On T3 interfaces, a periodic self test is run automatically. The cause of "main card BT crc error" messages is by the periodic self test on the unused port.

These messages can be ignored as they are harmless. Or, it's possible to loop back the interface so that the self test will not activate and the messages will not be logged. The local loopback might not able to solve the problem in some cases. In this situation, ignoring the message is the only remedy. See KB9382 - Example - How to prevent certain syslog messages from being written to the log file [juniper.net] for details on how to configure this.