What it means
A31902 (Encoder 1: SPI-BUS error occurred) signals an error when operating the internal SPI bus on the Sensor Module Encoder 1. The manuals describe the message in the same way for G130/G150 and for S120/S150, so one description covers both. Depending on the drive's configuration, the same condition can also be issued as a fault or with no reaction.
Why it appears
- An error occurred when operating the internal SPI bus of the Sensor Module Encoder 1.
- The alarm value belonging to the message is intended only for internal Siemens troubleshooting, so the manual names no further, on-site correctable cause.
What to check
- Replace the Sensor Module.
- If required, upgrade the firmware in the Sensor Module.
- Contact Technical Support.
Reading the message value
- The drive fills the message value with the alarm value stored in r2124.
- Interpret the value of r2124 in hexadecimal.
- The manual states this alarm value is only for internal Siemens troubleshooting; no bit decoding is given.
Parameters the manual names
- r2124 — alarm value: holds the value that belongs to this SPI-BUS error message; read it in hexadecimal. The manual notes it serves only for internal Siemens troubleshooting.
Acknowledging and restarting
In its alarm form, A31902 requires no acknowledgment. If the drive's configuration raises the same condition as a fault instead, it must be acknowledged immediately before the drive can be restarted. Acknowledgment does not remove the cause of the error — the Sensor Module steps above (replacement, firmware upgrade) are what address it.
The same on every family
Every manual that describes A31902 gives it the same reaction, acknowledgement and message class.
| Drive family | Reaction | Acknowledge | Message class | Component | Manual |
|---|---|---|---|---|---|
| S120, S150 | NONE | NONE | Hardware/software error (1) | Sensor Module Encoder 1 | SINAMICS S120, S150 List Manual · p. 3075 |
| G130, G150 | NONE | NONE | Hardware/software error (1) | Sensor Module Encoder 1 | SINAMICS G130, G150 List Manual · p. 1758 |
The drives this code lives on
A31902 is described for G130, G150, S120, S150. These are the converters of those families in our catalogue — price on request.
Questions technicians ask
What does alarm A31902 on a SINAMICS drive mean?
It reports an error when operating the internal SPI bus on the Sensor Module Encoder 1. The manuals print the same description for G130/G150 and for S120/S150.
How do I fix A31902?
Replace the Sensor Module, upgrade its firmware if required, and contact Technical Support. The alarm itself needs no acknowledgment; if the condition is raised as a fault, it must be acknowledged immediately.
What is the alarm value r2124 for A31902?
r2124 holds the alarm value belonging to the message and is read in hexadecimal. The manual states this value is only for internal Siemens troubleshooting.
Can A31902 also appear as a fault?
Yes. Depending on the drive's configuration, the same condition can also be issued as a fault or as a message with no reaction.
Codes next to this one
Source
Written from Siemens' own List Manuals and operating instructions; every number, designation and parameter on this page is checked against them before publication.
All SINAMICS codes: fault and alarm codes · the A31xxx group · SINAMICS manuals · Siemens manuals