CCG is the Centralized Clock Generator residing on CB, which failed in this case as logs indicated i2c and temp failure alarms for it.

Restarting CCG did not help. Chassisd does not recognize it.

Reference Logs:

Model: ptx5000

Junos: 21.2R3-S4.8

CCG 0. <<<<<< Missing from 'show chassis hardware'

CCG 1      REV 02  750-059802  ACPG3831     Clock Generator

> show chassis environment ccg 0 <------ shows power is disabled on this CCG.

The hardware swap of both routing engines and CBs were normal. This did include Junos upgrade from 17.4 to 21.2R3.

After the very last reboot, the below alarms showed.

admin@cr1> show system alarms

2 alarms currently active

Alarm time Class Description

2023-08-25 16:35:48 UTC Minor CCG 0 Temp Sensor Fail

2023-08-25 16:35:47 UTC Major No CG Online

CCG replacement resolved the issue.

Here are some reference links for this component:

https://www.juniper.net/documentation/us/en/hardware/ptx5000/topics/topic-map/ptx5000-chassis.html#id-ptx5000-centralized-clock-generator-description

https://www.juniper.net/documentation/us/en/hardware/ptx5000/topics/topic-map/ptx5000-troubleshoot.html#id-troubleshooting-the-ptx5000-centralized-clock-generators