Siemens SIMATIC S7-400 Hardware And Installation Manual page 176

Maintenance
Installing a New Module
1. Set the number of the rack at receive IMs.
2. Attach the new module of the same type and swing it downwards.
3. Screw the module on.
4. Fit the connecting cables.
5. Plug in the terminator, if applicable.
6. Secure the cover.
7. First switch on the power supply module in the ER.
8. Then switch on the power supply module in the CR.
9. Set the CPU mode switch to RUN mode.
How the S7-400 Behaves after Exchanging Modules
If an error occurs after replacing a module, you can read out the cause of the error
from the diagnostic buffer.
7-12
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S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01