Drive with caution — fix soon.
This code means the computer detects no usable activity from the upstream oxygen sensor on bank 1, as if the sensor signal is flat or absent. It's most often caused by a worn-out or unheated oxygen sensor, a broken heater circuit, or a wiring or connector problem. Replacing the oxygen sensor typically fixes it, and it's a common repair as sensors age.
$150 – $500
Varies by vehicle and root cause.
Usually yes for short trips. The car stays drivable, but with no working oxygen signal the computer can't optimize the fuel mixture, so fix it soon to protect fuel economy.
Typically $150 to $500. Most of the cost is the oxygen sensor and labor, though a simple wiring, fuse, or connector repair could be less expensive.
It's moderate severity. It won't usually strand you, but driving long-term with no oxygen feedback wastes fuel, raises emissions, and can stress the catalytic converter over time.
'No activity detected' usually means the sensor has aged out or its heater has failed, so it can no longer produce a usable signal. Once wiring and fuses are ruled out, replacing the sensor is the typical fix.