Qwiic STC31 CO₂ Sensor (SHTC3) – I2C Transceive Failed [Errno 121] Remote I/O Error

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1

I’m using the Qwiic STC31-based CO₂ sensor (Product ID: SFE-SEN-29260) with a Raspberry Pi 5 via Python. At the moment, I can successfully read CO₂ and temperature data from the STC31, but I cannot read anything from the SHTC3, and I consistently get the error: I2C transceive failed: [Errno 121] Remote I/O error.

With i2cdetect, the SHTC3 is detected at address 0x70, but when I try to read it in Python, I still get the same I/O error. I also lowered the I2C clock to 10 kHz, but it didn’t help. I tried debugging with a minimal I2C communication test script for the SHTC3, and it still fails with [Errno 121] Remote I/O error.

An AI assistant suggested cutting the I2C pull-up jumper on the back of the board as a last resort, but I’m concerned the SHTC3 might be faulty. Does anyone know an effective workaround or troubleshooting method for this issue?

2

Is anything else on the i2c bus? Can you share a photo of the setup/wiring?

3

Thanks for your reply. No—there is nothing else on the I2C bus. Only this Qwiic STC31 CO₂ sensor is connected to the Raspberry Pi 5 via a Qwiic cable. I’ve attached photos of the setup/wiring (Raspberry Pi side and sensor board side).

IMG_2149.HEIC
IMG_2149.HEIC3024×4032 2.15 MB

4

Sometimes Pis will have their internal i2c pullup resistors enabled (the sensor also has a pair), can you try ensuring they are disabled and re-check?