Can drive — fix at your convenience.
This code means the rear-most oxygen sensor on Bank 1 (Sensor 3) is reporting a high voltage, which the computer reads as a constant rich condition or a circuit fault. The usual causes are a worn or contaminated sensor, damaged wiring, a corroded connector, or an internal sensor short, and occasionally a genuinely rich-running engine. The most common fix is replacing the oxygen sensor or repairing its wiring.
$150 – $400
Varies by vehicle and root cause.
Generally yes, for the short term. This rear sensor handles emissions monitoring rather than engine control, so the car should run normally. Have it diagnosed within a week or two, and expect a failed emissions test until it's repaired.
Most repairs land between $150 and $400. The oxygen sensor is the biggest part of the cost, with labor depending on the sensor's location. If the fault is just wiring or a connector, you may pay less.
No, it's usually low-severity. The engine isn't at risk and the car drives normally, but it does affect emissions monitoring and can slightly lower fuel economy. It's worth fixing promptly so the car can pass inspection and the code doesn't mask another exhaust issue.
The rear oxygen sensor's voltage rises when it senses little oxygen in the exhaust, which the computer treats as a rich condition. A reading stuck high usually means the sensor is failing or has an internal short, though wiring problems can mimic it. A scan tool checking the sensor's live data confirms whether the sensor itself is the cause.