O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 1)

What does this mean?

Code P0134 means the PCM has detected no switching activity from the upstream O2 sensor on Bank 1, indicating the sensor may be dead.

Disclaimer: This diagnostic code is part of the standard OBD2 system and can apply to Gmc Sierra models manufactured from 1996 to 2026. However, please note that the presence of this specific code depends on your vehicle's exact engine configuration, options, and production year.