Troubleshooting ET200SP F-DI 6ES7136-6BA00-0CA0 Passivated Inputs

When an ET 200SP F-DI 8x24VDC safety input module (Siemens article number 6ES7136-6BA00-0CA0) appears to have every channel stuck in a passivated state — channel LEDs illuminate correctly, yet TIA Portal refuses to show live process values and a normal watch table shows no yellow quality code on the inputs — the fault is almost never a defective module. In the vast majority of cases the cause is either (a) the F-DI is not referenced by the safety program, or (b) the module has been derated out of its thermal envelope by a vertical mounting orientation in a hot enclosure. This technical reference walks the diagnostic tree, explains the PROFIsafe passivation mechanics behind the symptom, and gives the field-proven resolution path used on S7-319F systems.

1. Problem Statement and Field Symptoms

On an S7-319F-3 PN/DP F-CPU controlling eight operator panels, each with several safety I/O modules, the engineer observed the following on a vertical-mount rack:

• F-DI 8x24VDC HF (6ES7136-6BA00-0CA0) channel LEDs light as expected when a 24 V signal is applied to the field-side terminal.
• The TIA Portal project shows the module in the device configuration without configuration errors.
• When monitored in a standard (non-safety) watch table, the input tags do not update.
• Compared to a healthy module, the F-I/O DB shows every channel bit set to "passivated" (value "0" forced) even when the field wiring is removed.
• The yellow quality-code indicator normally seen on the left of a watch-table row for an F-tag is absent.
• Symptoms are now present on two of the eight panels, both of which share the trait of being among the last modules of a vertically installed ET 200SP rack.

Two distinct mechanisms are at play here: a PROFIsafe passivation behavior and a thermal derating condition. Both must be ruled out independently.

2. Root Cause Analysis

2.1 The F-DI Is Not Referenced by the Safety Program

Fail-safe inputs on Siemens F-CPUs are not freely readable from a non-safety watch table. The F-runtime group in the safety program is the only consumer that the F-I/O DB exposes. If a channel is configured in the hardware (HW Config / device configuration) but never used inside an F-FB / F-FC / safety main safety block, the input is treated as if it does not exist for the standard user program. TIA Portal simply does not update the tag, and the watch table shows no quality code at all (the row stays gray, not yellow). The first response in the original technical discussion captured this precisely: "If your F-DI's are not used in the safety program you can't see them in a variable-table."

This is by design. The F-CPU enforces the principle that fail-safe signals are only meaningful inside a certified safety function; the standard cyclic user program is intentionally blind to them.

2.2 Vertical-Mount Thermal Derating

ET 200SP modules are specified for two mounting orientations, and the ambient-temperature envelope is tighter for vertical installation. The relevant excerpt from the module manual states that for vertical mounting, the maximum permissible ambient temperature is reduced (typically to 40 °C from 60 °C for horizontal mounting on certain module variants). When the operating temperature of the module exceeds the derated limit, the module internally forces a passivation of all channels and reports a diagnostic interrupt to the F-CPU. Once the F-CPU logs the diagnostic event, the channel is held in the fail-safe state until the temperature returns to within range and a manual or automatic reintegration is executed.

Combined, the two conditions produce the reported symptom set: the F-DI is configured but unused by the safety program, and the mounting arrangement has already pushed the module into a derated thermal window where the F-CPU is logging temperature-related passivation diagnostics.

3. PROFIsafe Passivation — Underlying Mechanics

Passivation is a safety-integrity mechanism defined by the PROFIsafe bus profile. When an F-I/O channel is passivated, the channel no longer reports the live process value to the F-CPU. Instead, a fail-safe substitute value (always 0 for digital F-DI channels, 0 for digital F-DQ channels) is transmitted. Per the official Siemens safety reference, "In case of passivation, the F-I/Os will be switched into the fail-safe state. After fault correction, the F-I/Os can be reintegrated." See the manufacturer KB article Safety: Passivation and Reintegration of F-I/O (ID 22304119) for the canonical definition.

The same fail-safe substitution rule is mirrored in the TIA Portal documentation for the ET 200eco PN F-DI/F-DQ family: "If digital input channels are passivated, the fail-safe system always provides safe state values ('0') for the safety program." See Reactions to faults — TIA Portal manual collection.

The passivation state is communicated to the user program via the F-I/O DB. Each F-I/O DB has a standardized data layout with the following key fields:

Any value coming from the F-DI when PASS_ON = 1 is the substitute value, not the real process signal. The F-CPU is required to interpret this state inside the safety program; the standard user program may also read PASS_ON / QBAD to take non-safety actions (e.g., illuminate a maintenance lamp).

4. Why a Standard Watch Table Shows "Nothing"

The yellow quality-code column in a TIA Portal watch table signals a valid online value with a quality state. The colors map roughly to:

• Yellow — variable is online and updating, but the value is the fail-safe substitute (0) because the channel is passivated, or the value is a default initial value.
• Gray — variable is configured but not being updated by any online consumer; the F-CPU has no reason to refresh it because no safety block reads it.
• Red — connection error or invalid value.

On the 6ES7136-6BA00-0CA0 module in the field case, the watch table column is gray (no yellow). That is the diagnostic fingerprint of an F-DI configured in HW Config but not used by the safety program. It is not a hardware failure.

5. Mounting Orientation and Thermal Envelope

ET 200SP baseUnits and I/O modules support horizontal and vertical mounting. The maximum permissible ambient temperature for the F-DI 8x24VDC HF (6ES7136-6BA00-0CA0) depends on the orientation:

Always confirm the exact figure against the operating-instructions manual shipped with the module, as revisions of the article number may carry slightly different thermal limits. The vertical derating is enforced because convection cooling of the module is reduced when the heat sink fins are oriented vertically.

6. Diagnostic Procedure (Step-by-Step)

Use the following sequence to localize the root cause before changing any wiring or replacing any module.

1. Open the TIA Portal project online to the F-CPU (S7-319F-3 PN/DP). Confirm the diagnostic buffer is read; do not clear it yet.
2. Filter the diagnostic buffer for entries from the F-DI in question. Look for event IDs that map to channel passivation, temperature error, PROFIsafe communication error, or parameter assignment error.
3. Inspect the F-I/O DB for the affected module. Note the state of PASS_ON, QBAD, ACK_REQ, and the per-channel passivation bits in DIAG / channel status byte.
4. Search the safety program for the symbolic name of every input tag on this F-DI. Use Go To > Usage in the safety main safety block and in any F-FB / F-FC. If zero references are found, the input is configured but unused — this is the #1 cause of "no yellow in the watch table."
5. Measure enclosure ambient temperature at the F-DI mounting surface with a calibrated thermometer or the ET 200SP internal temperature sensor diagnostic (where supported by your configuration). Compare to the vertical-mounting limit from the module manual.
6. Inspect rack layout: confirm whether the module sits at the bottom or top of a vertical ET 200SP line, and whether the next module above / below is a high-power device (F-DQ relay output, motor starter, or 24 V power module with high dissipation).
7. Check the PROFIsafe address and slot in HW Config. Mismatched PROFIsafe addresses between the device configuration and the safety program cause persistent passivation with a CRC / watchdog fault in the diagnostic buffer.
8. Check the head module / interface firmware revision against the compatibility list in TIA Portal. A 6ES7155-6AU30-0BN0 IM 155-6 PN HF or later with the F-CPU bundle is required for the F-DI 6ES7136-6BA00-0CA0 to operate in PROFIenergy / PROFI-safe mode.

7. Resolution Path

The resolution depends on which of the two root causes is dominant in your installation.

7.1 If the F-DI Is Not Referenced by the Safety Program

1. Either remove the unused F-DI from the device configuration (preferred — keeps the PROFIsafe CRC computation small and reduces diagnostic noise), or
2. Add a minimal safety function that references the channel — for example, a pass-through F-FB that copies the input into a tag the user program can read, plus a discrepancy-time evaluation block.
3. Recompile the safety program and run an F-acceptance test (see Section 9).

7.2 If Vertical-Mount Thermal Derating Is the Cause

1. Move the affected F-DI to a horizontal position in the rack, or
2. Lower the enclosure internal temperature by adding cabinet cooling, relocating heat sources, or moving the panel out of direct sun, or
3. Use a wider thermal-budget module variant if available in the F-DI family.
4. After the corrective action, execute a manual reintegration of the channel (see Section 8).

8. Reintegration of the F-I/O

Reintegration is the act of moving a passivated channel back into the active, process-value-reporting state. Per the Siemens safety reference, this is only permitted after the original fault has been corrected. The F-CPU distinguishes two reintegration modes:

Manual reintegration code skeleton (SCL inside a safety FB):

// Reintegration handshake for an F-DI channel
IF ("F_IODB".ACK_REQ = TRUE) AND (Operator_Ack = TRUE) THEN
    "F_IODB".ACK     := TRUE;          // pulse to the F-I/O
    "F_IODB".ACK_REQ := FALSE;         // cleared by F-CPU after reintegration
END_IF;

On the F-CPU S7-319F, the ACK bit is pulsed for at least one F-runtime group cycle (default 100 ms) so that the F-I/O can complete the reintegration handshake over PROFIsafe.

9. F-Acceptance Test and Verification

After the corrective action, perform the F-acceptance test before returning the line to production:

1. Generate a fresh acceptance report in TIA Portal via Options > Safety > Generate acceptance report. The report must reflect the modified F-runtime group.
2. Force each input channel to "0" and "1" with a calibrated signal source. Verify the safety program reacts as documented in the F-FBD / F-LAD logic.
3. Disconnect a field wire to provoke a wire-break diagnostic. Verify the affected channel passivates and the safety program transitions to the safe state.
4. Restore the wiring. Verify that ACK_REQ rises and that a positive operator acknowledgment reintegrates the channel.
5. Repeat the test at the upper end of the cabinet's worst-case ambient to confirm the thermal margin.
6. Sign and archive the acceptance report per ISO 13849-1 / IEC 62061 project requirements.

10. Field-Proven Pitfalls

• Assuming the LEDs mean the channel is being read. The channel LED is a hard-wired indicator of the input voltage level; it has no relationship to whether the F-CPU is consuming the value.
• Trusting a healthy F-I/O DB comparison. A working F-I/O DB on another panel only proves the data layout is correct; it does not prove that this particular module's channels are wired to active safety functions.
• Forcing QBAD = 0 in the F-I/O DB. This bypasses the safety function and is flagged as a CRC violation by the F-CPU at the next F-cycle.
• Ignoring vertical-mounting temperature limits. The same module can run for years in a horizontal cabinet and start passivating the day the cabinet is rotated 90° for a layout change.
• Removing field connections as a "fix." The diagnostic will persist because passivation is a state of the channel, not of the wire.
• Asking the wrong support tier. Vendor hotlines occasionally treat F-I/O diagnostics as a normal-I/O problem and miss the safety-program reference dependency.

11. Quick Diagnostic Matrix

12. Summary

An ET 200SP F-DI 8x24VDC HF (6ES7136-6BA00-0CA0) that lights its channel LEDs but shows no values in a standard TIA Portal watch table is exhibiting a configuration-level symptom, not a hardware failure. Two root causes must be ruled out in order:

1. Is the F-DI actually consumed by a safety function in the F-runtime group? If not, the F-CPU will not publish the input to the standard watch table at all — the row stays gray.
2. Is the module's ambient temperature within the derated envelope for vertical mounting? If not, the F-I/O will be passivated by a temperature diagnostic, and the F-I/O DB will report PASS_ON = 1 / QBAD = 1 for every channel.

After correcting the root cause — either by adding the F-DI to a safety function or by restoring the thermal envelope — reintegrate the F-I/O via the standard ACK_REQ handshake and run the F-acceptance test before returning the line to production.

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