P0146 O2 Sensor Circuit No Activity Detected Bank 1 Sensor 3

P0146 indicates no activity from the bank 1 sensor 3 oxygen sensor circuit. The downstream signal remains too flat or inactive.

Code details

Generic OBD-II · P0

System: Fuel / Air
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not diagnose catalyst behavior until the no-activity oxygen sensor circuit is restored.

Symptoms of P0146

Check-engine light on, sometimes with rough or uneven running.
Hesitation, surging, or a noticeable change in fuel economy.
Occasionally hard starting or a smell of unburnt fuel.

Common causes of P0146

A failing or contaminated sensor (MAF, MAP, oxygen or air-fuel sensor).
Intake or vacuum leaks, or an exhaust leak near an upstream sensor.
Wiring, connector, or fuel-delivery problems that skew the reading.

Useful checks before replacing parts

Monitor bank 1 sensor 3 voltage during fuel changes, deceleration fuel cut, heater operation, and catalyst monitor conditions.
Check sensor signal circuit, heater feed, ground, connector fit, exhaust leaks, sensor contamination, and wiring near hot exhaust.
Verify the sensor is installed and connected at the expected bank 1 sensor 3 location.

Related OBD-II codes

These nearby fuel / air entries can help compare wording and pin down the fault area.