Installation manual
Publication 1394-IN002B-EN-P — February 2004
4-2 Troubleshooting Status Indicators
Troubleshooting System 
and Axis Module LEDs
The system module Status LED is visible from the front of the module. 
Refer to figures 2.1 and 2.2 for the location of the system module 
status LED.
If the System Module LED is: Potential Cause is: Possible Resolution is:
Steady red
Terminator not installed. • Install terminator.
Malfunctioning system module.
• Verify wiring.
• Secure wiring connections.
• Replace the module.
• Check logic supply ratings.
• Contact your local Allen-Bradley 
Support Representative.
Flashing red
A fault has occurred in the system 
(check for faults through the RSLogix 
5000, DriveExplorer, or the HIM).
• Reset faults.
• Verify wiring.
• Secure wiring connections.
• Check SERCOS fiber-optic 
connections.
Alternating red and green
DC bus is not up.  Apply three-phase power.
Open fuse or malfunctioning contactor 
on user-supplied 3 phase input.
• Check wiring to start/stop circuitry.
• Check the user program.
• Check fuse.
Malfunctioning system module. Replace the module.
Steady green The bus is up and axes are enabled. None needed.
Flashing green
The bus is up, but no axis is enabled.
• Check axes and enable them, if 
necessary.
• Verify that enable wiring is correct 
and not open.
Enable signal from position controller 
is not present.
• Check axes and enable them, if 
necessary.
• Verify that enable wiring is correct 
and not open.
• Check I/O connections on control 
board.
Controller has detected a machine 
system malfunction and will not enable 
the 1394.
• Check controller.
• Check the machine.
Not illuminated
There is no power to the system 
module.
• Check 24V ac/dc logic power 
supply.
• Check main ac input power supply.










