What it means
The manuals print this message under the title Encoder 1: I2C-BUS error occurred
. It is reported by the Sensor Module Encoder 1 and means that an error occurred while the internal I2C bus was being operated. The drive outputs the alarm value belonging to the message as its message value; it is stored in r2124 and is to be interpreted hexadecimal — the manual adds Only for internal Siemens troubleshooting
, so no decoding of the value is published. Depending on how the drive is configured, the same condition can also be output as a fault or simply as a message without any drive reaction instead of an alarm.
Why it appears
- An error occurred when the internal I2C bus of the Sensor Module Encoder 1 was being operated.
What to check
- Replace the Sensor Module Encoder 1.
- If required, upgrade the firmware in the Sensor Module.
- Contact Technical Support.
Reading the message value
- The drive writes the alarm value belonging to this message to r2124; the manual specifies that the value is to be interpreted hexadecimal.
- The manual publishes no decoding of this value: it states
Only for internal Siemens troubleshooting
.
Parameters the manual names
- r2124 — alarm value: read the value the drive has stored for this alarm here and interpret it hexadecimal. Because it is intended only for internal Siemens troubleshooting, it is chiefly relevant when you contact Technical Support.
Acknowledging and restarting
No acknowledgement is assigned to this alarm, so there is no reset step to perform; what resolves the message is the remedy itself — replacing the Sensor Module, upgrading its firmware if required, and contacting Technical Support if the case persists. The drive executes no automatic stop in response to this message. If the drive is configured to raise the same condition as a fault instead of an alarm, the manual specifies immediate acknowledgement for that fault.
The same on every family
Every manual that describes A31903 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
A31903 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 A31903 mean on a SINAMICS drive?
It is reported by the Sensor Module Encoder 1 and means that an error occurred while the module's internal I2C bus was being operated. Depending on the configuration, the same condition can also appear as a fault or without any drive reaction.
How do I clear alarm A31903?
The manual lists three steps: replace the Sensor Module, upgrade the firmware in the Sensor Module if required, and contact Technical Support. No other checks are described for this message.
What is stored in r2124 for A31903?
The alarm value of the message, which is to be interpreted hexadecimal. The manual states it is only for internal Siemens troubleshooting, so no decoding is published.
Does A31903 stop the drive or need an acknowledgement?
The drive executes no automatic stop in response to this message, and the alarm requires no acknowledgement. If the condition is configured as a fault, the manual specifies immediate acknowledgement.
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