P0166 - O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 3)

The oxygen sensor on bank 2 sensor 3 is not showing normal switching activity.

Code Overview

The oxygen sensor on bank 2 sensor 3 is not showing normal switching activity.

Common Causes

• Failed oxygen sensor
• Damaged wiring or connector near the exhaust
• Open or short in the sensor or heater circuit
• Exhaust leak or fueling issue affecting the reading

Diagnostic Steps

1. Inspect the sensor wiring and connector near the exhaust
2. Check live sensor data and heater operation
3. Look for exhaust leaks or related fuel-control faults before replacing parts

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

Browse the closest code-family pages when the same fault pattern often shows up nearby.

Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.