Core Issue
A Cisco 7500 series router may display log messages similar to these:
%CI-4-ENVWARN: 2.5 Reference measured at 1.99
%CI-2-ENVCRIT: +12 Voltage measured at 9.78
%CI-2-ENVCRIT: +5 Voltage measured at 4.12
%CI-2-ENVCRIT: -12 Voltage measured at -9.68
%CI-2-ENVCRIT: +24 Voltage measured at 19.06
While these messages seem to indicate a power supply issue, the actual issue may be a defective Chassis Interface (CI) board. This is because the CI handles the environmental monitoring.
Resolution
Errors similar to these could be a sign of a bad power supply or a bad CI:
If the 2.5 Reference measures this low (1.99), it is undoubtedly a CI problem. Reference voltages of 2.47 and higher are normal, while voltages below 2.47 indicate a CI problem.
If the router has two power supplies, and the combined bus voltages are low, it cannot be a power supply problem. This is because one power supply cannot drag down the output voltage of another due to the presence of isolation diodes. Suspect the CI in this case, as well.
If you have a spare power supply available, replace the one in the router. If the error messages remain after replacing the power supply, replace the CI.
For replacement instructions, refer to Replacing the CI Board in the Cisco 7500 Series Chassis.
For more information on power supply, fan, and CI troubleshooting, refer to the Step-by-Step Troubleshooting section of Hardware Troubleshooting for the Cisco 7500 Series Router.
