How to Resolve HW Config Consistency Errors 'Unable to Find Corresponding Object' on Redundant S7-400H Systems

In SIMATIC PCS 7 V6.0 redundant S7-400H systems (such as CPU 417-4H with redundant power supplies), the HW Config consistency error 'Unable to find corresponding object' occurring four times indicates that peripheral address gaps (e.g., addresses 16380 to 16383 marked with '?') or orphaned diagnostic cross-references exist between Rack 0 and Rack 1. If 'Save with Reorganization' fails with table lock errors on 'YDBS/YLinklist', the project database has lingering file locks. To resolve this, terminate all background STEP 7 processes, delete corrupted lock files, manually remove unassigned diagnostic address gaps in the Address Overview, and execute a clean consistency compilation.

Redundant Hardware Architecture and Cross-Rack Linking in S7-400H

In fault-tolerant SIMATIC PCS 7 systems, the S7-400H architecture consists of two symmetrical sub-racks: Rack 0 (Master) and Rack 1 (Standby), interconnected by high-speed fiber-optic synchronization modules.

To ensure bumpless master-standby failover:
* The STEP 7 hardware configuration database maintains internal relational tables (stored under [Project]\YDBS\) that pair identical hardware components across both racks: redundant power supply modules, CPU communication subnets, and Y-Link / redundant interface modules (IM 153-2).
* When an engineer copies sub-racks, deletes power supplies, or imports hardware fragments, cross-rack pointer tables can lose synchronization.
* During Station > Check Consistency, HW Config attempts to cross-reference every redundant object. If an object on Rack 0 points to a non-existent or misaligned partner on Rack 1, the compiler flags: Unable to find corresponding object.

Root Causes of 'Unable to Find Corresponding Object' Consistency Errors

Detailed forensic analysis reveals two primary triggers in legacy PCS 7 V6.0 projects:
1. Orphaned Power Supply and Diagnostic Addresses: Redundant power supplies (PS 407 10A) assign internal diagnostic addresses to report input power loss and battery failure to the CPU. If four power supplies are configured across the two racks and their diagnostic address assignments are deleted or modified without updating both racks symmetrically, HW Config loses the paired partner object.
2. Address Gaps with '?' in Address Overview: In HW Config, selecting View > Address Overview reveals reserved address bands (such as 16380 to 16383) assigned to undefined hardware modules with a question mark ?. These ghost entries represent unlinked diagnostic blocks that prevent consistency validation.

Resolving Peripheral Address Gaps Marked with '?' in Address Overview

To eliminate address gaps marked with ?:

Open Address Overview:
* In HW Config, select menu View > Address Overview....
* Inspect the Inputs and Outputs columns.
* Locate the specific address range reporting ? (e.g., bytes 16380 through 16383).
Identify Owning Hardware Modules:
* Typically, high addresses (above 16380) correspond to CPU integrated diagnostic addresses or redundant power supply monitoring.
* In the rack view, double-click each Power Supply module.
* Open the Addresses tab: confirm whether diagnostic addresses are enabled and verify that the assigned address range matches Rack 0 and Rack 1 symmetrically.
Reassign or Disable Diagnostic Addresses:
* If diagnostic addressing is not used, uncheck Diagnostic Interrupt in the power supply properties.
* If required, re-enter explicit, contiguous address numbers to clear the ? gap.

Clearing YDBS/YLinklist Database Lock Errors During Project Reorganization

When attempting to purge corrupted tables using File > Save As > With Reorganization (Slow), engineers often encounter:
Link management: unable to close the table .../Project/YDBS/YLinklist

The Cause: The database file YLinklist.dbf (which manages Y-Link and redundant PROFIBUS DP cross-references) is locked by an active Windows background process or an orphaned database lock file (.lck).
The Remedy:
1. Close SIMATIC Manager and all engineering tools.
2. Open Windows Task Manager: terminate processes s7tgtopx.exe, s7oemax.exe, and pdlrt.exe.
3. Navigate in Windows Explorer to the project folder: C:\Project\YDBS\.
4. Delete any files ending with .lck or ~tmp.
5. Relaunch SIMATIC Manager: Save As with Reorganization will now execute without table lock errors.

Step-by-Step Hardware Database Repair and Export/Import Workflow

If internal database corruption persists, execute the definitive hardware export/import repair:

Export Hardware Configuration:
* Open the problematic station in HW Config.
* Select menu Station > Export....
* Choose export format: Readable (CFG file) and save as HW_Repair.cfg.
Inspect and Sanitize CFG File in Text Editor:
* Open HW_Repair.cfg in Notepad++.
* Search for the invalid address range 16380 or corrupted link lines.
* Remove orphaned parameter lines corresponding to the missing diagnostic objects.
Import into Clean Station:
* In SIMATIC Manager, insert a temporary new S7-400H station.
* Open HW Config on the new station and select Station > Import....
* Select HW_Repair.cfg.
* Execute Station > Save and Compile. Consistency check will report 0 Errors.
Replace Faulty Station:
* Delete the corrupted station in the multi-project and replace it with the validated, repaired station.

Comparison of S7-400H Hardware Diagnostic Table States

The table below outlines common S7-400H hardware compilation consistency errors and their resolution.

Compiler Error StringSubsystem InvolvedRoot CauseResolution Pathway'Unable to find corresponding object'Redundant Racks (0 and 1)Asymmetric power supply or diagnostic address gapsAlign addresses in Address Overview'Table lock on YLinklist'Link Management (YDBS)Windows process locking database fileTerminate s7*.exe processes; delete .lck'Address gap with ?'Peripheral Address TableDeleted module leaving orphaned address reservationReassign addresses or export/import CFG'Synchronization module mismatch'Sub-rack Fiber ModulesAsymmetric slot assignment of fiber sync cardsEnsure sync modules occupy slots 7/8 on both racks

Verification

To confirm that HW Config consistency is fully restored:
1. In HW Config, select Station > Check Consistency.
2. Verify that the compilation log window reports: Check consistency: 0 Error(s), 0 Warning(s).
3. Open View > Address Overview: confirm that no address ranges display with a question mark ?.
4. Execute Station > Save and Compile. Confirm that the hardware configuration compiles cleanly into the block folder.
5. Perform an online download: PLC > Download to Module > Changes Only. Confirm the running CPU accepts the download in RUN mode without entering STOP.

Limitations and Operational Precautions

Never execute a full hardware download to an active production S7-400H system; always verify that changes can be downloaded via 'Changes Only' to prevent an unexpected plant trip.
In redundant S7-400H systems, both sub-racks must be identical in physical chassis model, power supply wattage, and CPU firmware revision.
Before editing raw .cfg export files, always create a timestamped backup copy of the original project.
Do not attempt manual file deletions inside the YDBS folder while SIMATIC Manager is open.

Engineer FAQ

Why did the error appear four times specifically?

In an S7-400H system with redundant power supplies, each rack contains two power supply modules (four power supplies total). If diagnostic addresses were assigned and then corrupted, each of the four power supplies generated an individual 'Unable to find corresponding object' consistency error.

What does the YDBS folder contain?

YDBS (Y-Link Data Base System) stores internal relational tables linking redundant DP master systems, Y-Links, and cross-rack synchronization objects in fault-tolerant automation stations.

Can I download changes if consistency check has errors?

No. STEP 7 strictly prohibits downloading hardware configurations that fail consistency checks, as inconsistent hardware tables can trigger controller fatal faults.