Drive with caution — fix soon.
This code means the bank 2 sensor 3 oxygen sensor signal is essentially flat, with no detectable activity, so the computer can't use it to monitor the exhaust. This commonly results from a failed sensor, a non-working sensor heater, or an open in the wiring or connector. The usual fix is replacing the oxygen sensor, but wiring, connector, and heater circuit faults should be checked first.
$150 – $400
Varies by vehicle and root cause.
Usually yes, since an inactive rear sensor mainly affects emissions monitoring rather than drivability. Short trips are generally fine, though fuel economy may drop a little. Aim to have it diagnosed within a week or two so the sensor can resume its monitoring job.
Most repairs fall between $150 and $400, covering the oxygen sensor and roughly an hour of labor. If the cause is just a fuse, connector, or section of wiring, it can be cheaper. A proper diagnosis confirms whether the sensor itself needs replacing.
It's a moderate concern. The vehicle stays drivable and safe, but without a working sensor the computer can't monitor that part of the exhaust, and you won't pass an emissions test. Fixing it promptly is the right move, though it's not an emergency.
It means the sensor's signal stays flat instead of fluctuating as it should when reading the exhaust. That can happen because the sensor has died, its heater never warms it up, or the wiring is broken, so the computer simply sees nothing useful coming from it.