P0146
O2 Sensor Circuit No Activity Detected Bank 1 Sensor 3
Oxygen sensor (fuel & air)
Generic OBD-II
Medium
What it means
P0146 means the oxygen sensor on bank 1, sensor 3 (a downstream monitoring sensor on vehicles with a third O2 sensor) is showing no activity — its signal isn't switching as it should. Because this is a monitoring rather than fuel-control sensor, the engine runs and starts normally; the practical impact is a check-engine light and an incomplete emissions monitor.
Medium
Can I keep driving? Yes — this is a downstream monitoring sensor, so the engine runs and starts normally; the main impact is on emissions monitoring.
Common symptoms
What you'll notice
- Check-engine light on
- Emissions-readiness monitor won't complete
- Failed emissions/smog test
- Little to no change in how the car drives
Common causes
Most likely first
- Faulty oxygen sensor (bank 1, sensor 3)Likely
- Open, corroded, or damaged wiring/connector at the sensorCommon
- Blown fuse or heater-circuit fault leaving the sensor inactiveCommon
- Exhaust leak near the sensorLess often
- Failed ECM/PCM (rare)Less often
How to diagnose & fix
Work through it in order
- Check the bank 1 sensor 3 signal in live data — 'no activity' means it isn't switching.
- Inspect the sensor connector, wiring, and related fuse for opens or corrosion.
- Verify the sensor's heater circuit has power and ground.
- Look for exhaust leaks near the sensor that could disturb its reading.
- Replace the oxygen sensor if it stays inactive. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0146?+
Yes. This is a rear/monitoring oxygen sensor, so drivability is essentially unaffected. The concern is emissions — it will keep the readiness monitor from completing and cause an emissions failure.
Can I just clear P0146?+
It returns once the ECM runs the O2 monitor again and sees no sensor activity. Repair the sensor or its circuit first.
Related codes
Often seen with P0146
Read & clear P0146 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX