ET 200SP BaseUnit Type: Resolving DI Module Hardware Faults

Resolving SIMATIC ET 200SP 'Hardware Component Removed' Faults Caused by BaseUnit Type Mismatch

When commissioning a SIMATIC ET 200SP distributed I/O station against an S7-1200 CPU, engineers frequently encounter the diagnostic entry "Hardware component removed or missing" together with process-image update errors of the form "New I/O access error during process image update, input X (Y bytes) will temporarily not be updated as part of the updating of PIP 0". The most common cause on a freshly wired and configured station is a mismatch between the physically installed BaseUnit color/type and the BaseUnit type selected inside the TIA Portal device configuration. This reference walks through the failure mode observed with two DI 16x24VDC ST modules, identifies the root cause, and provides the exact configuration procedure required to clear the fault.

1. Affected Hardware and Firmware Scope

The symptom pattern was reproduced on the following component combination, which is a typical entry-level PROFINET configuration for S7-1200 systems:

The IM 155-6 PN BA (6ES7155-6AA00-0BN0) supports up to 12 I/O modules and a maximum of 32 bytes of input/output data on the PROFINET side. When expanding to more than 12 modules or when using F-modules, you must migrate to the IM 155-6 PN ST (6ES7155-6AU00-0BN0) or the IM 155-6 PN HF (6ES7155-6BA00-0CN0). The BaseUnit fault described here is independent of the IM variant and applies to all ET 200SP stations.

For hardware specification and ordering data, refer to the SIMATIC ET 200SP product page and the ET 200SP Catalog and Overview (PDF).

2. Observed Diagnostic Entries

With two DI 16x24VDC ST modules inserted on physically identical light-color BaseUnits, the following entries appear in the CPU diagnostic buffer and online diagnostics:

Fault: Hardware component removed or missing
  HW_ID = 271
  Slot: 2 (second DI module)

CPU error: New I/O access error during process image update
  Input 2 (2 Bytes) will temporarily not be updated as part of the updating of PIP 0
  HW_ID = 279 - Object management system

CPU error: New I/O access error during process image update
  Input 4 (2 Bytes) will temporarily not be updated as part of the updating of PIP 0
  HW_ID = 280 - Object management system

Fault: Hardware component not available due to a parameter assignment error
  HW_ID = 280

The HW_ID values are assigned automatically by TIA Portal and depend on the slot position and module order. Reordering modules, renaming devices, or recompiling hardware will renumber the HW_IDs. The diagnostic IDs themselves are stable and map to the standard S7 diagnostic IDs:

3. Root Cause: BaseUnit Color/Type Mismatch

The ET 200SP BaseUnit is not just a passive backplane carrier; it also determines how the 24 V DC supply rail (P1/P2) and the AUX bus are routed across slots. There are two functionally distinct BaseUnit families and they are color-coded:

• BaseUnit type A0 / suffix "D" — light terminal box: Opens a new potential group. The supply voltage for the next module(s) must be fed into this BaseUnit. After this BaseUnit, a fresh isolated 24 V segment begins.
• BaseUnit type B0 / suffix "B" — dark terminal box: Conducts/continues an existing potential group. No new supply is wired here; the module is supplied from the previous light BaseUnit's potential group through internal jumper contacts.

The naming convention is: BU15-P16+A0+2B (15 mm wide, 16 process terminals, AUX terminal A0 present, 2 bridges, B-type, dark) versus BU15-P16+A0+2D (same terminals, D-type, light). The "B" stands for "durchgehend" / "continuing" and the "D" for "Durchgang"/"opening" in the German naming tradition. The visual cue is the color of the terminal block cover: light gray = opens new potential group, dark gray = continues the previous group.

4. Why the Fault Only Appears with Two or More Modules

With a single DI module the entire station is one potential group. Both "light" and "dark" BaseUnit types default to functioning because the topology constraints are not yet violated. As soon as a second module is added, the slot ordering creates an implicit assumption: a module inserted after a dark BaseUnit is electrically supplied by the previous light BaseUnit's 24 V group. If the second slot is configured as "light" in TIA Portal but the physical BaseUnit is "dark", or vice versa, the parameter assignment fails because the supply path the controller expects does not match the wiring:

1. Slot 1: configured as "opens new potential group" (light) — physical BaseUnit is light. Supply wired to terminals 1B/2B. Module powers up.
2. Slot 2: configured in TIA as "opens new potential group" (light) — physical BaseUnit is also light. Both modules want their own isolated supply. If only one supply is wired, slot 2 reports "parameter assignment error". If supply is wired, the station boots but TIA Portal's slot list still mismatches the project, producing the "removed/missing" diagnostic.
3. The PROFINET device goes into degraded state; PIP 0 inputs of slot 2 freeze at zero. Subsequent slots fail identically because their HW_IDs depend on the slot list resolving correctly.

The error is purely a project/parameter mismatch — the modules and BaseUnits are electrically healthy. Replacing modules, swapping to digital output modules, or trying different slot orders will not fix the root cause. Only the BaseUnit type selection in the device configuration must be corrected.

5. Step-by-Step Resolution in TIA Portal

Prerequisites

• TIA Portal V15 or later (procedure identical through V18; menu labels unchanged).
• STEP 7 Professional license for the ET 200SP HSP (Hardware Support Package) installed.
• Online connection to the CPU or offline project matching the wired hardware exactly.

Procedure

1. Identify physical BaseUnit color. Look at the terminal block cover between the module and the DIN rail. Light gray = D-type (opens new potential group). Dark gray = B-type (continues).
2. Open the project. In the project tree, expand Devices & networks > [ET 200SP station] > Device view.
3. Click each BaseUnit slot in the device view. The Inspector pane on the right shows the BaseUnit catalog assignment.
4. Match catalog selection to installed hardware. Right-click the BaseUnit icon and choose "Change device / variant" or "Replace device". Select the exact MLFB printed on the side of the installed BaseUnit. The catalog distinguishes:
   • 6ES7193-6BP..-....B → dark, continues group
   • 6ES7193-6BP..-....D → light, opens group
5. Verify the supply flag. In the BaseUnit properties, the checkbox "New potential group" (German: "Neue Potenzialgruppe") must be:
   • Checked for slot 1 and any slot after which you physically wire a new 24 V feed.
   • Unchecked for every intermediate slot whose module is supplied through the previous light BaseUnit's jumper.
6. Recompile the hardware configuration: right-click the CPU → "Compile > Hardware (rebuild all)".
7. Download the HWCN to the CPU/IM and confirm the prompt "Overwrite diagnostic buffer".
8. Power-cycle the ET 200SP station if the IM is still in degraded state.

For the canonical Siemens configuration procedure, see the Configuring ET 200SP chapter in the TIA Portal Help (cloud documentation). The ET 200SP system manual also documents the BaseUnit selection matrix in the section "Installation / BaseUnits".

6. Verification

After the corrected HWCN is downloaded, verify the station is healthy through four independent checks:

If the diagnostic buffer is clear but inputs still read zero, force the input via the hardware test (24 V applied to terminal, observe LED, read IW) to confirm the wiring before chasing software issues.

7. BaseUnit Selection Reference

The following matrix covers the most common BaseUnit families for ST (standard) modules. F-modules use a separate family (BU..F) with screw-type or push-in terminals color-coded differently (always yellow AUX for fail-safe).

Rule of thumb: every time the supply wiring changes (new 24 V source, new isolation point, group shutdown), insert a light BaseUnit. Everywhere else, use a dark BaseUnit. Mixing them incorrectly produces the diagnostic pattern described in section 2.

8. Diagnostic Flowchart

9. Related Configuration Pitfalls

Beyond BaseUnit type, several adjacent misconfigurations produce overlapping or identical diagnostic patterns. Address these before assuming hardware is defective:

9.1 Wrong Slot for the Server Module

The server module (6ES7193-6PA00-0AA0) is mandatory at the right end of the ET 200SP station to terminate the backplane bus. If it is missing or in the wrong slot, the IM reports "Station failure" rather than "module removed", but downstream slots still show "removed" because the bus is broken. Insert the server module in the last slot before closing the station with the right end cap.

9.2 IM 155-6 PN BA Limitations

The 6ES7155-6AA00-0BN0 (BA variant) supports only the ST module family. Inserting an F-module (e.g. DI 16x24VDC F) on a BA IM produces "parameter assignment error". Migrate to 6ES7155-6AU00-0BN0 (ST) or 6ES7155-6BA00-0CN0 (HF) for F, HS, or R1 modules.

9.3 HSP Version Mismatch

If the TIA Portal project uses an older HSP than the firmware on the IM, "module removed" diagnostics appear after download. Match the IM firmware version in the project (Inspector > Module parameters > "Module" tab) with the actual firmware reported under "Online > Accessible devices".

9.4 PROFINET Device Name

Until the PROFINET device name is assigned via "Assign PROFINET device name", the IM stays in identification state and the slot list is invisible to the controller, which may report HW_ID 271/279/280 for every configured slot. Use the topology editor or the "Assign device name" tool from the IM's online context menu.

10. Specifications Cross-Reference

11. Frequently Asked Questions