That manual action may be restoring or triggering communication, but it does not identify the failed hop. Trace the path from the OS runtime through the configured network to the CPU, then test each hop after a cold start.
Which hop stops before SIMATIC Manager goes online?
Separate the OS computer, the network path, and the controller in your diagnosis. The operator buttons depend on a working runtime and communication path; they may appear in the graphics while their commands cannot reach the controller. Opening an online session from SIMATIC Manager can coincide with recovery, but that alone does not prove that the OS requires an engineering connection.
| Observation after power-up | Likely area to check | Evidence to collect |
|---|---|---|
| OS runtime or project is not running | OS startup and project/runtime configuration | Whether the runtime starts automatically; startup messages or errors |
| Runtime is active, but CPU data is unavailable | Network interface, route, or configured connection | OS and CPU addresses, subnet settings, interface state, connection diagnostics |
| Data is available, but operator buttons do not act | Command path, tag configuration, or controller logic | Whether the associated tag changes and whether the CPU receives the command |
Record what works before and after opening the engineering connection. Note whether values update, whether buttons become effective, and whether the OS runtime itself restarts. This distinguishes a communication recovery from a runtime startup problem.
Does the OS computer restore its network link after power returns?
Check the physical path first: confirm that the OS network adapter is enabled, the cable and switch link are present, and the intended interface is connected to the controller network. If the CPU and OS host connect through intermediate network equipment, check link state at each hop. A link light proves only a physical connection, not correct addressing or application communication.
Compare the configured OS and CPU network settings with the approved project/network plan. Confirm that each address belongs to the intended subnet, the selected adapter is the one used by the runtime connection, and no other device is using either address. A changed address, duplicate address, or different active adapter can make the same project work only after an engineering connection selects or activates another communication path.
| Check | Compare | Decision |
|---|---|---|
| OS address and subnet | Configured values against the network plan | Correct subnet and intended adapter? |
| CPU address and subnet | Configured values against the CPU/network configuration | Reachable on the intended path? |
| Other interfaces and routes | Active adapters and routes before and after restart | Is traffic leaving through the expected interface? |
| Address uniqueness | Configured addresses against other devices | Any duplicate or changed assignment? |
Do not alter addresses by trial and error. Preserve the working configuration and capture the settings both before and after a restart; the comparison can reveal what “network changes” means in this system.
Is the OS runtime ready before its controller connection?
Check the OS host’s startup behavior independently of the CPU. Confirm that the intended PCS 7 OS project and runtime start automatically after the computer restarts, and inspect startup or runtime diagnostics for failures. A runtime that is not running cannot serve the operator screens regardless of CPU reachability.
Next, inspect the configured controller connection in the project and the runtime’s communication status. Verify that it points to the intended CPU and uses the intended network interface. Compare the loaded project/runtime configuration with the configuration intended for the installed system. Do not treat a successful SIMATIC Manager online connection as proof that the OS project’s own connection is configured correctly: engineering communication and OS runtime communication are separate paths.
Check whether the CPU reaches RUN after power-up and whether the OS connection recovers without an engineering session. Record CPU state and OS communication status at startup and after the manual online action. These observations show whether the dependency is CPU startup, OS startup, or connection recovery.
How can you isolate a connection that recovers only after going online?
- Start from a known, recorded configuration. Capture OS and CPU addresses, subnet settings, active network adapters, CPU operating state, and OS runtime state.
- After a controlled power cycle, do not immediately open SIMATIC Manager. Check the physical link, confirm that the OS runtime is running, and inspect the OS connection status.
- Test reachability between the OS host and the CPU using the site’s approved diagnostic method. If basic reachability fails, resolve the interface, addressing, route, or physical path before changing project communication settings.
- If reachability succeeds but OS data remains unavailable, inspect the OS project’s configured controller connection and runtime diagnostics. Compare the target CPU and selected interface with the installed network configuration.
- Open the engineering connection only after recording the failed state. Observe whether CPU state, OS runtime state, network settings, or connection status changes at that moment.
- Change one identified cause at a time, then repeat the same restart test. Keep a record of the setting changed and the result.
If the OS already reads live values but buttons fail, check whether a button action changes its associated tag and whether that command reaches the controller. If the tag does not change, inspect the screen object and tag configuration. If the command reaches the CPU but produces no machine action, investigate the controller logic and interlocks separately. Do not troubleshoot a button as a network fault until you establish which stage fails.
What proves the fix survives a cold restart?
Use a controlled restart test that reproduces the reported power-up condition. Confirm in order that the CPU reaches its intended operating state, the OS computer restores the intended network interface and settings, the OS project/runtime starts, and its controller connection returns without opening SIMATIC Manager. Then verify that live data updates and test an approved operator command while observing its tag or controller response.
Repeat the check after another restart if the first result is ambiguous. A fix is not established by a single successful online session: the acceptance check is automatic OS-to-CPU communication and working operator functions after restart, with no manual engineering connection required.
What happens if the OS works only after SIMATIC Manager connects?
What happens if the OS works only after SIMATIC Manager connects?
That action may restore a communication path or coincide with CPU/runtime recovery; it does not by itself identify the cause. Record CPU state, OS runtime state, interface, and connection status before and after connecting, then isolate which one changes.
What happens if the CPU is reachable but WinCC shows no live data?
Check that the OS runtime is running and that its configured connection targets the intended CPU through the intended interface. Basic network reachability does not prove the OS runtime connection is correct.
What happens if live values return but the buttons still do not work?
Observe the button’s associated tag and determine whether its command reaches the CPU. A tag that does not change points toward the screen object or tag configuration; a command received by the CPU shifts diagnosis to controller logic or interlocks.
What happens if the network seems to change after power loss?
Compare the OS and CPU addresses, subnet settings, active adapter, and routes before and after restart. Check for a duplicate address or a different selected interface before changing the project configuration.
Final verification: After a controlled restart, confirm the CPU is in its intended state, PCS 7 OS runtime is active, live data updates, and an approved button command reaches the controller—all without connecting through SIMATIC Manager.