12-34
Keyswitch mismatch after switchover
Allen-Bradley · Logix 5000
What does 12-34 mean?
Immediately after a switchover, the keyswitch positions of the primary and secondary controllers are mismatched. Specifically, the old primary is in Program mode and the new primary is in Run mode.
Common Causes
- Keyswitch positions of primary and secondary controllers mismatched after switchover
- Old primary controller in Program mode, new primary in Run mode
Repair Steps & Checklist
Click steps to track your progress.
- 1
Change the keyswitches from Run to Program to Run mode twice to clear the fault.
- 2
Use the Logix Designer application to go online with the controllers, then clear the faults and change both the controllers' modes to Run.
Verified technical data. Last updated: March 2026
Related Faults
Source: Logix 5000