What it means
The ECU detects a general electrical fault on the third O2 sensor in the bank 2 exhaust path (typically post-second-cat in multi-cat exhausts).
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 2 Sensor 3 is a third oxygen sensor in the bank 2 exhaust path, where fitted, often farther downstream than Sensor 2. P0163 indicates a general electrical fault in that sensor's circuit, so the ECU cannot rely on its signal as expected.
Common causes
Most likely first.
- Sensor aged or failed
- Sensor wiring open or shorted
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Read freeze-frame and live data to identify whether Bank 2 Sensor 3 has a missing, implausible, or erratic signal.
- Confirm that the vehicle is equipped with a Bank 2 Sensor 3 and locate it in the exhaust path before inspecting its wiring.
- Inspect that sensor's connector and harness for exhaust heat damage, corrosion, loose pins, or an open or shorted wire.
- Check the sensor's power, ground, and signal circuit against the manufacturer's specification.
- If the circuit tests correctly, assess Bank 2 Sensor 3 itself for failure.
Common fixes
- Reconnect or clean the Bank 2 Sensor 3 connector.
- Repair damaged, open, or shorted sensor wiring.
- Restore a poor power or ground connection in the sensor circuit.
- Replace Bank 2 Sensor 3 if its circuit is intact but the sensor fails testing.
Can I keep driving?
The car is usually driveable, but the fault can interfere with emissions monitoring and may increase fuel use. Arrange diagnosis soon, and stop driving if the engine runs severely poorly or the warning light flashes.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.