Troubleshooting Siemens 6ES7223-1PH32-0XB0 DIAG LED SM 1223 Not

Troubleshooting the Siemens 6ES7223-1PH32-0XB0 DIAG LED: SM 1223 Module Not Detected

The Siemens 6ES7223-1PH32-0XB0 is the SM 1223 digital signal module (DI 8 x 24 V DC / DQ 8 x Relay) for the SIMATIC S7-1200 system. A common field complaint involves a blinking DIAG LED and the module being absent from the TIA Portal device view after a CPU factory reset. This reference walks through root cause analysis, hardware wiring, software configuration, and verification to bring the module online.

1. Problem Description

Engineers commissioning an S7-1214 DC/DC/DC CPU with a 6ES7223-1PH32-0XB0 SM 1223 report the following symptoms:

• The SM 1223 module is absent from the TIA Portal project tree and device view (online diagnostics shows the CPU only).
• The DIAG LED on the SM 1223 blinks red (or in some cases blinks green after a TIA Portal download).
• The user has connected +24 VDC to the 1L and 2L terminals on the SM 1223 but the module still does not appear online.
• Whether X10 and X11 terminals must be connected is unclear.

2. SM 1223 (6ES7223-1PH32-0XB0) Module Overview

The 6ES7223-1PH32-0XB0 is the 8-point digital input / 8-point relay output variant. It is one of several SM 1223 SKUs; verify the exact MLFB on the side label of the physical module before applying any procedure in this article.

2.1 Why the module has two power terminals

The SM 1223 has two electrically isolated groups:

• Group 1 (inputs): Powered through 1L and 1M. This 24 V DC rail powers the input optocouplers and any source/sink input sensors.
• Group 2 (relay outputs): Powered through 2L and 2M. This 24 V DC rail feeds the relay coils on the output side.

Both groups must receive 24 V DC for the module to fully power up, but the DIAG LED and backplane communication will still initialize as long as the module receives backplane power from the CPU and at least one group supply is present. Verify both 1L/1M and 2L/2M are powered if any outputs will be exercised.

3. Understanding the DIAG LED

The DIAG LED on the SM 1223 is the primary on-board status indicator. State decoding (consistent with the S7-1200 System Manual):

4. Root Cause Analysis

The dominant root causes for "SM 1223 absent + blinking DIAG" are listed below in descending order of occurrence:

1. No hardware configuration downloaded. The CPU was reset to factory settings, which clears all configuration. The SM 1223 in slot 1 (or whichever slot is wired) must be added in the device view and the project downloaded.
2. Sensor/load power supply missing or reversed. Without 24 V DC at 1L/1M the input section is dark and group diagnostics can flag a supply fault.
3. Module not physically seated. The SM 1223 must be locked onto the CPU's right-side bus connector until the slider audibly clicks.
4. Firmware mismatch. The SM 1223 firmware must be compatible with the CPU firmware. For a 1214C with firmware V4.x, the SM 1223 firmware V3.0 or later is required.
5. Defective module. Rare; usually only after electrical overstress on the relay contacts or supply transients.

5. Hardware Wiring Requirements

Confirm the following wiring before any software step. Reference the official wiring matrix at SM 1223 wiring diagrams (Siemens documentation).

5.1 Required Power Connections

5.2 X10 and X11 Clarification

X10 and X11 are CPU sensor-supply terminals on S7-1200 CPUs (not on the SM 1223 itself). They provide a switched 24 V DC source that can be used to power sensors directly from the CPU, eliminating the need for an external terminal block in compact installations. They are not required for SM 1223 backplane communication. If sensors are powered from a separate 24 V DC supply, X10/X11 need not be wired.

5.3 Wiring Diagram (SM 1223 6ES7223-1PH32-0XB0)

The SM 1223 has a removable terminal block on top. Field-side wiring is identical in concept to the wiring diagrams published in the S7-1200 manual collection. Typical 24 V DC wiring:

+24V ----[ 1L ]----  (input group supply)
GND  ----[ 1M ]----  (input group return)
+24V ----[ 2L ]----  (relay coil supply)
GND  ----[ 2M ]----  (relay coil return)

   I0.0..I0.7 ---- sensor switches ---- 1M
   Q0.0..Q0.7 ---- load contacts (dry, NO relay)

6. Step-by-Step Recovery Procedure

6.1 Prerequisites

• CPU in STOP or factory-reset state.
• 24 V DC supply capable of sourcing at least 150 mA for the SM 1223 plus load current.
• TIA Portal project with the correct CPU order number (e.g., 6ES7214-1AG40-0XB0 for a 1214 DC/DC/DC).
• Ethernet cable (or PROFIBUS/PROFINET path depending on the CPU variant).

6.2 Procedure

1. Open the project in TIA Portal.
2. In the Project Tree, expand Device Configuration > [CPU].
3. Look at the CPU's right side rail. The catalog on the right shows available SM modules. Locate SM 1223 DI 8 x 24 V DC / DQ 8 x Relay (MLFB 6ES7223-1PH32-0XB0).
4. Drag the SM 1223 into slot 1 of the CPU rack.
5. Right-click the CPU > Compile > Hardware (rebuild all).
6. Connect the programming PC to the CPU (direct Ethernet or via switch).
7. Click Download to device > Hardware and software (only if different).
8. Confirm the dialog. The CPU will STOP, load the new configuration, and re-start in RUN if configured to do so.
9. Observe the SM 1223 DIAG LED: it should change from flashing red/green to steady green within a few seconds after RUN.
10. Open Online & Diagnostics on the SM 1223 slot. Confirm the module is now visible with module order number, firmware, and I/O status.

6.3 Verification

• DIAG LED = steady green.
• SM 1223 appears in the online accessible devices list with its module name.
• CPU diagnostic buffer shows a single informational entry for module insertion/configuration, no errors.
• In Watch table or program, force an input: the corresponding I-address (e.g., I0.0 byte-aligned per slot) toggles.
• If a relay output is exercised, the contact closes and the per-point output LED illuminates.

7. Diagnostic Buffer Reading

If the DIAG LED remains red after the configuration download:

1. In TIA Portal, go Online > Online & Diagnostics on the CPU.
2. Open the Diagnostic buffer.
3. Look for entries containing the slot number of the SM 1223. Common entries:

8. Power Supply Verification

Use a multimeter to confirm the supply rails at the module terminals, not at the supply itself. There can be a significant drop across terminal connectors and fuses.

9. Firmware Compatibility Matrix

To check the SM 1223 firmware online: Online & Diagnostics > Module Information. To upgrade, use TIA Portal's Online > Accessible devices and select Online & Diagnostics > Firmware Update.

10. Extended Troubleshooting Matrix

11. Common Field Mistakes

• Confusing CPU sensor supply with module supply. X10/X11 (CPU) are not a substitute for 1L/2L (module).
• Reversed polarity on 1M/2M. Some SM 1223 variants have reverse-polarity protection, others do not — always confirm with the module's label.
• Exceeding relay contact ratings. Driving inductive DC loads (solenoids, contactors) without a snubber will shorten relay life.
• Mixed module types in slot 1. Adding an analog SM instead of digital by mistake. TIA Portal will detect this and flag a configuration error.
• Forgetting to stop the CPU before download. If the project does not match the connected module topology, TIA Portal may refuse to download without the right consent prompt.

12. Safety Notes

• De-energize the 24 V DC supply before inserting or removing the SM 1223. The bus connector does not support hot-swap on all CPU firmware levels.
• Relay outputs can switch hazardous voltages (up to 250 V AC). Follow local electrical codes and lock-out / tag-out procedures.
• Separate power groups (1L and 2L) must have their grounds tied only at a single point if different potentials are used.

13. Replacement Procedure (if module is faulty)

1. Stop the CPU.
2. Power down the supply rails to the SM 1223.
3. Open the terminal block release flaps and remove the field-side connector.
4. Slide the bus connector release lever downward.
5. Pull the module straight off the CPU.
6. Install the replacement in the reverse order, observing the MLFB exactly.
7. Restore power, download the hardware configuration if needed, and verify the DIAG LED turns green.

14. Glossary

• MLFB: Machine-Readable Product Code (Siemens order number).
• DIAG LED: Combined diagnostic indicator.
• Group (input/output): A set of channels that share a common supply rail.
• Backplane: The internal bus between CPU and signal modules.