Power unit: I2C bus error occurred

What does F30903 mean?

This fault signifies a communication error on the I2C bus, typically with an EEPROM or an A/D converter within the power unit. The fault value (r0949) provides specific detail: 80000000 hex indicates an internal software error, while 00000001-0000FFFF hex points to a module fault. This can lead to incorrect readings, configuration issues, or unreliable operation. The risk is complete or partial failure of the affected module.

• Loose or corroded I2C bus connection between the power unit microcontroller and internal peripherals (e.g., EEPROM, A/D converter).
• Electromagnetic interference (EMI) disrupting I2C data lines due to inadequate shielding or grounding within the power unit assembly.
• Internal component failure (e.g., EEPROM chip, A/D converter IC) causing data corruption or a bus lock-up condition.
• Power supply instability (e.g., 3.3VDC or 5VDC regulator) for the I2C bus components leading to unreliable communication.

Click steps to track your progress.

1. 1

   De-energize the power unit and verify secure seating of all internal ribbon cables and connectors on the control board.

2. 2

   Measure the I2C bus pull-up resistor values (typically 2.2kΩ or 4.7kΩ) on the power unit control board using a multimeter.

3. 3

   Inspect the internal power unit PCB for signs of heat stress, component damage (e.g., swollen capacitors), or solder joint cracks near I2C bus components.

4. 4

   Using an oscilloscope, monitor the SDA and SCL lines of the I2C bus for proper waveform integrity and signal levels (e.g., 0V to 3.3V or 5V transitions).

5. 5

   Check the stability of the auxiliary voltage supplies (e.g., +3.3VDC, +5VDC) feeding the I2C bus components on the power unit using a multimeter.