Publication 1756-UM523F-EN-P - December 2006
Maintain and Troubleshoot the System        105
2. Wait several minutes for the system to try to synchronize. What 
do the CNB modules in the primary chassis show?
• PwQS — Stop. Your system is synchronized.
• PwDS — Go to step 3.
3. Use this table to troubleshoot the secondary chassis.
4. Wait several minutes for the system to try to synchronize. Do the 
CNB modules in the primary chassis show PwQS?
• Yes — Stop. Your system is synchronized.
• No — Go to Troubleshoot a Failure to Synchronize on 
page 105.
Troubleshoot a Failure to 
Synchronize
To troubleshoot a failure to synchronize, perform this procedure.
If the SRM module 
has a
And a secondary CNB 
module
And a secondary controller 
has a
Then
Green OK LED 
Indicator
Does not show NET ERR Flashing Red OK light Clear the major fault of the controller.
It is possible that you have to clear the fault on 
both the primary and secondary controllers.
Solid Red OK light A. Cycle the power to the chassis.
B. If the OK light remains solid red, replace the 
controller and flash the controller with the 
appropriate revision of firmware.
Solid Green OK light Go to step 4.
Shows NET ERR  ⇒ Check all ControlNet taps, connectors, and 
terminators for proper connections.
Red OK LED Indicator  ⇒ A. Cycle the power to the chassis.
B. If the OK light of the SRM module remains 
solid red, contact your local distributor or 
Rockwell Automation representative.
IMPORTANT
• If the steps in this section do not correct the situation, check the 
usage of the CNB modules. See Adjust CPU Usage for a CNB Module 
on page 123.
• If the chassis still doesn't synchronize, try to manually synchronize it. 
See Manually Synchronize the Chassis on page 118.