Siemens troubleshooting answers
20 questions with answers cited from the manufacturer manuals.
- 0S7-1500 OB122 I/O access error (16#42) in RUN, what to check?
An OB122 I/O access error on a Siemens S7-1500 CPU indicates a problem during direct access to I/O data, such as reading from an input module. The CPU will remain in RUN and log a diagnostics buffer entry. A 16#42 fault …
- 0S7-1500 CPU in STOP with OB121, Fault_ID 16#3A after partial download, what to check?
An S7-1500 CPU in STOP mode with OB121 and Fault_ID 16#3A indicates a programming error, specifically an attempt to access a data block (DB), function (FC), or function block (FB) that is either not loaded or does not ex…
- 0S7-1500 OB86 Rack Error: PROFINET device keeps dropping off, why?
An OB86 Rack Error on a Siemens S7-1500 indicates a failure or return of a DP master system, PROFINET IO system, DP slave, or IO device. Unlike S7-300/400, the S7-1500 CPU defaults to staying in RUN mode if OB86 is not c…
- 0Siemens S7-1500 CPU in RUN, OB82 diagnostic interrupt, what to check?
An OB82 diagnostic interrupt on a Siemens S7-1500 CPU indicates a change in a diagnostics-capable module's status, a power supply/battery backup error, or a memory error. Unlike older S7 models, the S7-1500 CPU remains i…
- 0Siemens S7-1500 OB80 Time Error: Cycle Time Exceeded, what to check?
An OB80 Time Error on a Siemens S7-1500 CPU means the cyclic program or an interrupt OB ran longer than the maximum configured cycle time. While the CPU continues after the first overrun with OB80 present, a second overr…
- 0SINUMERIK 840D sl alarm 25050 during contouring, what to check?
Alarm 25050, "Axis contour monitoring," on a SINUMERIK 840D sl indicates that an axis's actual position deviates from the expected position by more than the defined contour tolerance (MD36400). This typically occurs duri…
- 0SINUMERIK 840D sl alarm 25040: axis moves at standstill, what to check?
Alarm 25040 on a SINUMERIK 840D sl indicates that an axis, which should be stationary, has moved beyond its allowed position tolerance. This monitoring activates after a delay once interpolation has finished. Common caus…
- 0SINUMERIK 840D sl Alarm 25000, active encoder hardware fault: what to check?
Alarm 25000 on a SINUMERIK 840D sl signifies a hardware fault with the active encoder, meaning its signals are missing, out of phase, or have a ground/short circuit. This causes the NC to switch the axis to follow-up mod…
- 0SINAMICS G120 A07910: Motor overtemperature alarm, what to check?
The SINAMICS G120 A07910 alarm indicates that the motor's measured temperature (KTY sensor) or thermal model has exceeded the alarm threshold (p0604), or a PTC/bimetal contact has responded. This is an alarm, not a fault…
- 0SINAMICS G120 F07900: Motor blocked on start, what to check?
The F07900 fault on a SINAMICS G120 indicates the motor has operated at its torque limit for longer than the configured delay time (p2177) while remaining below the speed threshold (p2175). This often points to a mechani…
- 0SINAMICS G120 CU240E-2 F07801 at start, what to check first?
The F07801 fault on a SINAMICS G120 drive indicates that the permissible motor limit current was exceeded. This often occurs at start, during acceleration, or on a load step. Common causes include switching onto a rotati…
- 0SINAMICS G120 trips F30005 after running a while, what to check?
Fault F30005 on a SINAMICS G120 indicates that the Power Module has been overloaded, meaning its I2t value (r0036) reached 100%. This typically happens when the permissible rated current is exceeded for too long or the l…
- 0SINAMICS G120 CU240E-2 F30003 during running, what to check?
Fault F30003 on a SINAMICS G120 indicates that the Power Module has detected an undervoltage condition in the DC link and has shut down. This can occur during operation if the supply voltage dips or fails, during brownou…
- 0SINAMICS G120 F30002 during ramp-down, what to check?
A SINAMICS G120 F30002 fault indicates a DC link overvoltage, meaning the Power Module detected too much voltage and tripped. This often happens during ramp-down, especially with high-inertia loads, due to regenerated en…
- 0SINAMICS G120 F30001 instantly at power-on, r0949=1: what to check?
Fault F30001 on a SINAMICS G120 indicates an overcurrent detected by the Power Module, causing an OFF2 trip. The fault value r0949 helps identify the phase involved, with bit 0 corresponding to phase U. An instant trip a…
- 0Siemens LME11 blinks 10 times after replacing the unit, what to check?
A Siemens LME series gas burner control blinking red 10 times indicates a wiring error, an internal fault, or a problem with its output contacts. This fault can occur at any point in the sequence, often after wiring work…
- 0Siemens LME 7 blinks: flame loss during operation, what to check?
A Siemens LME control showing 7 red blinks indicates too many losses of flame during operation. This means the flame was established but then lost while the burner was running, exceeding the allowed repetitions. For LME1…
- 0Siemens LME21 blinks 5 times and locks out after a minute, what to check?
A Siemens LME21 gas burner control blinking 5 times indicates an 'Air pressure switch time supervision' fault. This means the air pressure switch was already in its working position when the burner control expected it to…
- 0Siemens LME 4 blinks: extraneous light at startup, what to check?
A Siemens LME burner control showing 4 red blinks and a green-red signal lamp during startup indicates extraneous light. This means the flame detector reported a flame before any fuel valves opened, which is a startup pr…
- 0Siemens LME21 2 blinks: No flame at end of safety time, what to check?
A Siemens LME21 controller displaying 2 red blinks indicates that no flame was established by the end of the safety time (TSA) after the fuel valve opened and ignition was attempted. This is a non-alterable lockout on LM…