What it means
A33903 — Encoder 3: I2C-BUS error occurred is raised when an error occurs while operating the internal I2C bus of the Sensor Module Encoder 3. Depending on the drive's configuration, the same condition can also be issued as a fault (F) or without a reaction (N).
Why it appears
- An error occurred when operating the internal I2C bus on the Sensor Module Encoder 3.
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 outputs a message value (placeholder %1) together with this alarm.
- The alarm value is stored in r2124 and must be interpreted in hexadecimal.
- No decoding of the value is printed — it serves only internal Siemens troubleshooting, so there is nothing in it for the service technician to evaluate.
Parameters the manual names
- r2124 — alarm value: holds the value behind this alarm; read it in hexadecimal. The manual notes it is only for internal Siemens troubleshooting.
Acknowledging and restarting
As an alarm, A33903 triggers no drive reaction and requires no acknowledgement. If the drive's configuration raises the same condition as a fault (F) instead, the printed reaction is still NONE, but the fault must then be acknowledged immediately; as N, there is likewise no acknowledgement.
The same on every family
Every manual that describes A33903 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 3 | SINAMICS S120, S150 List Manual · p. 3177 |
| G130, G150 | NONE | NONE | Hardware/software error (1) | Sensor Module Encoder 3 | SINAMICS G130, G150 List Manual · p. 1848 |
The drives this code lives on
A33903 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 A33903 mean on a SINAMICS drive?
It is the alarm 'Encoder 3: I2C-BUS error occurred': the Sensor Module Encoder 3 has detected an error when operating its internal I2C bus.
How do I fix A33903?
The manual's remedy is to replace the Sensor Module and, if required, upgrade its firmware, then contact Technical Support. As long as the code appears as an alarm, no acknowledgement is needed.
What is the alarm value r2124 for A33903?
The drive stores the alarm value for this code in r2124, and it must be interpreted in hexadecimal. The manual states the value is only for internal Siemens troubleshooting, so no decoding is published.
Does A33903 stop the drive?
No. The reaction printed for this code is NONE, both as alarm and as fault; only when it appears as a fault must it be acknowledged immediately.
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 A33xxx group · SINAMICS manuals · Siemens manuals