OBD codes / P0163
P0163
ModerateO2 Sensor Circuit Low Voltage (Bank 2, Sensor 3)
You can drive with P0163 without worry — this far-downstream sensor is a monitor, not a controller. Plan the fix around your emissions-testing schedule, and have any nearby exhaust rattle or leak looked at during the same visit since a leak can be the actual cause.
What this code means
This code reports that the third oxygen sensor on bank 2 — a position that exists only on vehicles with a second catalytic converter on that side — is stuck reporting low voltage, the electrical signature of an endlessly lean exhaust. Sitting after two converters, this sensor sees the most thoroughly cleaned exhaust in the system and has no role in fueling the engine, so the code is about monitoring integrity rather than performance. A pinned-low signal usually means the sensor has failed, the signal wire is shorted to ground somewhere along its long underbody run, or an exhaust leak just upstream is letting fresh air wash over the tip. Because outside air reads as lean, even a small leak at a flange or gasket near the sensor can hold the signal down.
Symptoms you might notice
- Check-engine light and nothing else in most cases
- Failed emissions inspection
- No drivability changes to speak of
What it costs to fix
Typical range: $100–$450 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| O2 sensor (Bank 2, Sensor 3) | $30–$200 | ~0.3–1 hrs |
| Wiring or connector repair | $5–$60 | ~0.5–1.5 hrs |
| Exhaust leak repair (gasket or flange) | $15–$100 | ~0.5–1.5 hrs |
Rear-of-vehicle sensors are usually easy to access, keeping labor short. Rust is the main cost driver — both for freeing a seized sensor and because rusted exhaust joints near the sensor are a common source of the leaks that trigger this code.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0163 for my exact vehicle →
Frequently asked
Can an exhaust leak really cause P0163?
Yes. Exhaust pulses can draw outside air in through a leak, and oxygen-rich outside air reads as lean — which drives the sensor voltage low. A leak at a flange or gasket just upstream of the sensor is a known cause worth checking before replacing anything.
Do I even need this third sensor?
Your vehicle was certified with it, so yes — the computer expects it, and the check-engine light will stay on without it. It exists to verify the second catalytic converter on that bank is working, which only matters for emissions, but that includes passing inspection.
How do I know which sensor is Bank 2, Sensor 3?
Bank 2 is the cylinder bank without cylinder 1, and Sensor 3 is the last sensor in that bank's exhaust path, after the second catalytic converter — typically the sensor furthest toward the rear of the vehicle on that side. A model-specific diagram removes the guesswork.
Is the fix for P0163 expensive?
Usually modest. Downstream sensors tend to be the cheaper ones, access at the rear of the exhaust is generally good, and a wiring or exhaust-gasket fix can cost even less than a sensor. The exception is a badly rusted exhaust that fights the repair.
Seeing P0163 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0163 for my vehicleRelated trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0163 from your phone — see our honest guide to the best OBD2 Bluetooth adapters.
Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.