P0165 — O2 Sensor Circuit High Voltage (Bank 2 Sensor 3)
Drive with caution — fix soon.
What P0165 means
This code sets when the voltage from the bank 2 sensor 3 oxygen sensor stays too high, which can mean the sensor sees a constantly rich exhaust or that the signal wire is shorted to power or the sensor's reference is faulty. This downstream sensor supports emissions and catalytic converter monitoring. It's most often fixed by replacing the oxygen sensor, though wiring shorts, connector issues, or a genuine rich fuel condition should be checked first.
Common symptoms
- Check engine light is on
- Slightly reduced fuel economy
- Failed emissions or smog test
- Possible fuel smell or rich running if the mixture is off
- Persistently high oxygen sensor voltage on a scan tool
Common causes
- Faulty bank 2 sensor 3 oxygen sensor
- Signal wire shorted to voltage or to another circuit
- Corroded or contaminated sensor connector
- Rich fuel condition from leaking injectors or other faults
- Coolant or oil contamination of the sensor
Typical repair cost
$150 – $400
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0165 code?
Usually yes for short trips, since this rear sensor mainly affects emissions monitoring. If you smell raw fuel or the engine runs roughly, a rich condition may be involved and you should get it checked sooner. Otherwise a diagnosis within a week or two is fine.
How much does it cost to fix a P0165 code?
Most repairs cost between $150 and $400, primarily the oxygen sensor plus about an hour of labor. If the real cause is a wiring short or a fuel system issue, the price can shift. Proper diagnosis avoids replacing a sensor that isn't actually bad.
Is a P0165 code serious?
It's generally a moderate concern. The vehicle remains drivable, but a persistent rich condition behind the high voltage can waste fuel and, over time, harm the catalytic converter. At the very least it will keep you from passing emissions, so plan to fix it.
Does high voltage mean the engine is running rich?
It often does, because a high oxygen sensor voltage typically reflects a rich exhaust. However, the same high reading can come from a wire shorted to power or a contaminated sensor. A technician will review fuel trims and inspect the wiring before concluding whether it's the mixture or the sensor.