S7-1200 TIA Portal V11 Error 0604:000137: Diagnostic and Recovery

Overview: What Event 0604:000137 Means on the S7-1200

Event 0604:000137 is a diagnostic-buffer entry written by an S7-1200 CPU that has gone to STOP (or is being held out of RUN) after a request to override the priority class of the currently executing organization block (OB) could not be satisfied. The format follows the Siemens convention used across the SIMATIC S7-1200 and S7-1500 families:

• Class (0604) – Identifies the family of events tied to OB execution and priority class handling.
• Event ID (000137) – Identifies the specific event within that class.

When the field text of the event is shown in the TIA Portal diagnostic buffer, the text associated with this event is rendered approximately as "This CPU cannot override requests" (English translation of the German/regional text). The same root cause manifests on the engineering station as a project that downloaded previously, then surfaces a popup, refuses to open OB1, and in some cases terminates the TIA Portal process (most often reported on TIA Portal V11 SP2 and older V11 service packs). Because V11 SP2 predates many of the stability fixes introduced in V12, V13, and later, the same event encountered on a current TIA Portal release is rarely a TIA Portal crash; it is a CPU diagnostic event that must be cleared at the controller.

Why TIA Portal V11 SP2 Is the Common Thread

TIA Portal V11 was the first release to integrate STEP 7, WinCC, and Startdrive into a single engineering environment for the S7-1200. Service Pack 2 (V11 SP2) added several bug fixes for hardware configuration uploads from the S7-1200, but field reports from that era show recurring issues that match this error pattern:

For a controller that has been in service for years, the same symptom now appears when an engineer opens a long-archived V11 SP2 project in a modern TIA Portal and attempts to do an online comparison or download to the same CPU. The S7-1200 firmware on the controller, the project on disk, and the TIA Portal version are no longer in agreement on what OB1 should contain.

Root Cause Tree for Event 0604:000137

Event 0604:000137 is the CPU's statement that it received a request to start a higher-priority OB while a lower-priority OB was running, and the CPU could not perform the required priority-class override. The four root causes observed in the field, ranked by frequency on the S7-1200 family, are listed below.

Prerequisites Before Recovery

1. Confirm TIA Portal version. If the project was last saved in V11 SP2, the TIA Portal installation on the maintenance PC must be at least V11 SP2 Update 5 or later. Earlier V11 builds will not open the project reliably.
2. Verify the S7-1200 CPU order number and firmware version. Read the CPU's front-panel label and the diagnostic buffer to record the firmware version (typical values for the V11 SP2 era: V2.0.x through V3.0.x; current S7-1200 V4 CPUs are not supported by V11 SP2).
3. Archive the project. Use Project > Archive to produce a .zap archive. Save the archive to a network share that is not on the engineering station's local drive.
4. Take a full online backup. Connect to the CPU, then go to Online > Backup from online device (in V11 SP2: Online > S7-1200 station > Backup). This captures the current OB1, the data blocks, the hardware configuration, and the retentive state.
5. Document the wiring. A recovery that includes a hardware reconfiguration will not succeed without an up-to-date wiring diagram. Confirm the I/O address assignment before changing any device configuration.

Step 1 – Read the Diagnostic Buffer

The diagnostic buffer on the S7-1200 is the authoritative record. Anything in the project tree, the OB1 view, or the popup is secondary. Use the following sequence to read it without opening the project file (this avoids the TIA Portal crash on OB1):

1. In TIA Portal, switch to the project view and select the S7-1200 station in the project tree.
2. Choose Online > Go online and select the correct PG/PC interface (PROFINET or PROFIBUS, depending on how the CPU is connected).
3. Open Online & diagnostics from the CPU's context menu.
4. Select Diagnostics > Diagnostic buffer.
5. Read the most recent entries top-down. Event 0604:000137 should be visible. Note the timestamp, the operating mode transition (RUN → STOP, or STOP → RUN attempt), and any associated OB start information.
6. Save the buffer to a text file with Save as. This file is the evidence you will use to drive every subsequent decision.

Sample diagnostic buffer entries you may see surrounding event 0604:000137:

09:25:14.317  2014-05-03  CPU 1214C DC/DC/DC  RUN -> STOP   request from OB
09:25:14.318  2014-05-03  Event 0604:000137  "CPU cannot override requests"
09:25:14.319  2014-05-03  OB82 (diagnostic interrupt) cannot be started
09:25:14.320  2014-05-03  OB1 priority class conflict detected

Capture the entries above the 0604:000137 line, because they are almost always the actual cause. The 0604:000137 line is the consequence.

Step 2 – Evaluate the CPU Operating State and Perform a Memory Reset

If the CPU is in STOP and will not transition to RUN, perform a memory reset (MRES) before changing the project. MRES clears the work memory and the retain area, which forces the CPU to re-read OB1 from the load memory (MMC or internal flash) on the next download.

1. Turn the mode selector to STOP.
2. Hold the selector in the MRES position for at least 3 seconds until the STOP LED flashes slowly.
3. Release, then turn the selector to MRES again within 3 seconds. The STOP LED flashes faster as the reset runs.
4. Wait for the STOP LED to become solid. The CPU is now in factory-default state with no user program.

After MRES, attempt to bring the CPU to RUN with the empty project. If the CPU stays in STOP with a different diagnostic event, the controller hardware itself is suspect; proceed to Step 3 anyway to confirm the engineering toolchain is not the cause, then escalate to hardware replacement.

Step 3 – Repair or Replace OB1

The OB1 source is the most common failure surface. The repair depends on whether a clean copy of OB1 exists.

Option A – Clean copy of OB1 exists in the project or a backup

1. Go offline in TIA Portal.
2. Right-click Program blocks > OB1 and select Delete (only). Do not delete the rest of the program blocks.
3. Use Online > Compare offline/online to confirm the CPU no longer has an OB1 to compare against.
4. Drag the clean OB1 back into Program blocks from the backup folder or the online backup archive.
5. Compile the project. If compilation completes without errors, proceed to Step 4.

Option B – No clean copy exists

1. Create a new OB1 in the project (TIA Portal will generate a default priority class and interface).
2. Re-implement the cyclic logic from the most recent validated backup. If the logic is only in a PDF or paper printout, this is the time to commission a new development environment before the controller is returned to service.
3. Set OB1 priority class to 1 (cyclic) unless the application explicitly requires a different class. The S7-1200 supports priority classes 1 (lowest) through 26 (highest); OB1 is class 1 by default.
4. Compile and proceed to Step 4.

Step 4 – Verify the Hardware Configuration

A hardware configuration that does not match the plugged modules is the second most common cause. The V11 SP2 upload flow in particular is known to lose signal module entries when more than four SMs are present, and to lose signal board (SB) entries entirely.

1. Open the Device configuration of the S7-1200 station.
2. Compare the rack view against the actual rack. Confirm:

• CPU order number and firmware version.
• Signal board (SB) on the CPU front, if any (SB 1221, SB 1222, SB 1223, SB 1231, SB 1232).
• Signal modules (SM) in slots 1 through 8 (SM 1221, SM 1222, SM 1223, SM 1231, SM 1232, SM 1234).
• Communication modules (CM) and communication processors (CP).

3. Open Properties > System constants for every module and confirm the I/O addresses match the wiring diagram.
4. Compile the hardware configuration. Address overlaps and missing modules will be reported as compile errors at this point; fix them before attempting to download.

Step 5 – Resolve Firmware and TIA Portal Version Mismatch

The S7-1200 firmware and the TIA Portal version must agree. Common mismatches in the field:

1. Read the CPU firmware from the diagnostic buffer or the front-panel display (the CPU order number ends in the firmware version, e.g., 6ES7214-1AE30-0XB0 for V3.0).
2. Compare with the TIA Portal version's compatibility table. A TIA Portal version that does not list the firmware version cannot perform a download; it will reject the operation at the connect stage.
3. If a downgrade is required (e.g., the CPU is V2.x and the project was last touched in V14), install TIA Portal V13 SP1 on a maintenance PC dedicated to this controller family. The S7-1200 V2.x and V3.x CPUs are no longer supported by current TIA Portal versions.

Step 6 – Project File Recovery Options

If TIA Portal V11 SP2 crashes when opening the project, restore the project from the highest-fidelity source available, in this order of preference:

1. Online backup taken in Prerequisites, step 4 (most complete, includes retain values).
2. Project archive (.zap) on the engineering file share.
3. Source export (TIA Portal V11 SP2: Options > Source files > Export).
4. Print archive (PDF of OB1, FB, FC, DB contents).

For a corrupted .ap11 / .ap12 project, the file is a ZIP-like archive. To extract the OB1 source without opening the project, use the following:

// Linux / Git Bash or PowerShell with Expand-Archive
unzip "./Project_archive.ap11" -d ./project_extracted
cat ./project_extracted/ProgramBlocks/OB1.xml | head -200

This step is for forensics only; do not attempt to patch the XML and reload it. Re-create OB1 in TIA Portal from the extracted source and download cleanly.

Step 7 – Full CPU Reset and Re-Download

1. Power down the S7-1200 rack. Wait 10 seconds.
2. Power up, confirm the CPU is in STOP with no diagnostic events for 30 seconds. If event 0604:000137 still appears with no project loaded, the CPU is failing self-test; replace the CPU.
3. Connect with TIA Portal. Confirm Online > Accessible nodes shows the CPU.
4. Perform a Download to device. In V11 SP2, this is Online > Download to device; tick Overwrite all in the dialog.
5. Watch the diagnostic buffer live. The download should produce a single clean RUN transition. Any 0604:000137 entry during the download means the priority class attribute of OB1 was written incorrectly; stop, recompile OB1 with priority class 1, and re-download.

Step 8 – Verification Checklist

Long-Term Path: Migrate Off TIA Portal V11 SP2

TIA Portal V11 SP2 is out of mainstream support and is not compatible with the S7-1200 V4.x CPUs, the S7-1500 family, or any current SINAMICS drive or SIMATIC HMI panel. The engineering risk of staying on V11 SP2 is the lack of patch coverage for known instabilities, not just for event 0604:000137 but for project file handling in general. The recommended migration path is:

1. Identify all S7-1200 CPUs in service and their firmware versions.
2. For V2.x and V3.x CPUs that cannot be upgraded, retain one TIA Portal V13 SP1 maintenance installation for legacy support, and use a separate TIA Portal V18 (or current) installation for V4.x CPUs and any new work.
3. Use TIA Portal's project upgrade tool to migrate the V11 SP2 project to V13 SP1 first, then to the current version. Skipping the intermediate upgrade is not supported for the S7-1200 family.
4. Document the migration. Event 0604:000137 is rarely seen on V13 SP1 and later because the OB1 attribute handling was rewritten in V12 SP1.

Preventive Measures

• Lock the OB1 priority class to 1 in the project template. A priority class change on OB1 is the single largest contributor to 0604:000137 events.
• Run Online > Compile > Software (rebuild all blocks) on every saved revision. This forces a clean write of the OB1 header and prevents incremental corruption.
• Perform an online backup after every successful download. The backup is the only source that contains the exact binary the CPU is running.
• Avoid interrupting a download to the S7-1200 at the moment the LED pattern indicates OB1 is being written (slow alternating RUN/STOP flash). If interrupted, perform a memory reset and re-download from the most recent online backup.
• Schedule a periodic (annual) diagnostic buffer review. A pattern of 0604:000137 entries on a controller that has been stable for years is the leading indicator of a deteriorating MMC or signal module.