This article describes the root cause behind the ACX box alarm PEM 0 Not OK and the steps to follow before concluding that this is a hardware issue.

The ACX1100, ACX2100, and ACX2200 platforms generate a PEM 0 Not OK alarm and log the following messages:

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lab@SKSIVA# run show chassis alarms 
1 alarms currently active
Alarm time               Class  Description
2015-07-24 09:46:13 UTC  Major  PEM 0 Not OK


Jul 24 09:46:13  send: red alarm set, device PEM 0, reason PEM 0 Not OK
Jul 24 09:49:10 CHASSISD_SNMP_TRAP6: SNMP trap generated: Power Supply failed (jnxContentsContainerIndex 2, jnxContentsL1Index 1, jnxContentsL2Index 0, jnxContentsL3Index 0, jnxContentsDescr PEM 0, jnxOperatingState/Temp 6)
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 The PEM 0 not OK alarm in the ACX1100, ACX2100, and ACX2200 platforms is generated for the following reasons:

• The routers have two power inputs, Input 1 and Input 2, and both are built into the router.
• If either input is not connected to the power source, then the router generates this alarm.
• If both inputs are connected to the power source and one of the power inputs doesn't receive the power feed, then the router generates this alarm.
• This alarm is generated even if either power feed is unstable or there is no steady power feed in the circuit.

This feature was introduced on these routers to indicate that the router is running on a single power source without any redundancy in the power supply.

When we see this alarm on the ACX1100, ACX2100, and ACX2200 platforms that have a built-in power module, perform a generic check of the power source, power cables, and so on:

1. Check whether both power inputs are connected to the power source.
2. Check the power cables for any damage.
3. Even if connected, make sure that the power feeds are properly positioned on the inputs.
4. After checking all of the above, if you still see the PEM 0 not OK alarm, open a case with JTAC.
5. JTAC will help determine whether this is an internal power module failure and an RMA needs to be requested.