In the complex world of industrial automation, Siemens drives (ranging from the venerable Masterdrives to the modern Sinamics S120, G120, and S150 families) are known for their robustness. However, like any precision electronic equipment, they occasionally halt production with an error code. Among the more cryptic and frustrating alarms for maintenance technicians is Siemens drive fault code 7902.
If you are staring at a panel displaying “F07902” or “Fault 7902,” you know production has stopped. This article provides a deep dive into what this fault means, why it occurs, and—most importantly—a step-by-step guide to getting your machinery back online. siemens drive fault code 7902
| Root Cause | Solution |
|------------|----------|
| PLC in STOP | Set PLC to RUN or reconfigure drive to ignore missing telegram (p2040 = 0 – not recommended for safety) |
| p2040 too short | Increase p2040 to at least 2–3× bus cycle time |
| Loose connector | Reseat or replace bus connector |
| Wrong telegram type | Match p0922 with PLC configuration (e.g., standard telegram 1 for speed control) |
| No termination | Activate termination on both ends of PROFIBUS segment |
| EMI | Check cable routing, add ferrites, verify shield grounded at both ends |
| Faulty option board | Replace communication board (e.g., CBE20 for PROFINET) | Decoding Siemens Drive Fault Code 7902: Causes, Diagnostics,
| Cause | Description |
|-------|-------------|
| PLC stop | Controller switched to STOP mode, stopped sending cyclic data |
| Cable issue | PROFIBUS/PROFINET cable disconnected, damaged, or poorly terminated |
| Connector fault | Loose or broken fieldbus connector (especially PROFIBUS 9-pin D-sub) |
| Configuration mismatch | Telegram configuration (e.g., telegram type, length) differs between drive and PLC |
| Bus overload | Excessive bus cycle time or high bus load causing intermittent telegrams |
| Parameter error | p2040 (telegram monitoring time) set too low |
| Master failure | Fieldbus master (PLC) power cycle or hardware fault |
| Interference | Electromagnetic interference (EMI) on bus cable | Fault response: TRIP (F)
Status bit: ZSW1
Disconnect drive terminals and measure resistance at room temperature. Should be ~600Ω. Use a hairdryer to warm probe—resistance should increase smoothly.