However, the PEM LED can be red due to external or environmental issues, even if the PEM is working fine.
Hardware failure or power surge due to lightning strike.
A red LED on the PEM is typically an indicator of a failed power supply. But to be certain, review any strange occurrences that took place prior to it becoming red.
If the facility suffered a lightning strike that knocked out the power and the router comes back up, the LED may be red. Before assuming that it is a failed PEM, try powering the PEM off and then back on. If it is working properly, it should come back on with the LED in the green state. From this point, monitor the situation to see if you have further issues with the PEM. If you do, open a case with JTAC.
If there were no abnormal occurrences, prior to the LED becoming red or if it is red after powering the PEM off and then back on, then try reseating the PEM followed by trying it in a different slot. If neither of these resolves the issue, then open a case with JTAC.