O2 Sensor Circuit (Bank 2 Sensor 2)

What it means

The engine computer has found an abnormal signal from the bank 2 downstream oxygen sensor, which monitors that bank's catalytic converter on V6 and V8 engines. Engine performance is usually unaffected, but the computer can no longer monitor the converter.

Related codes: P0157P0158P0159P0160P0161P0430

Symptoms3

• Check engine light on, usually with no other symptoms.
• Bank 2 catalytic converter self-test does not complete.
• Failed emissions test.

Possible causes5

• Wiring or connector under the car damaged by heat, water or stones.
• Failed bank 2 downstream oxygen sensor.
• Downstream sensor connectors of the two banks swapped by mistake.
• Exhaust leak near the sensor.
• Sensor heater fault.

How to diagnose5

1. Identify the correct sensor; on some cars the two bank pipes join after the converters, so confirm the right one with the manufacturer information.
2. Compare its signal with the bank 1 downstream sensor on a scan tool.
3. Inspect the wiring and connector under the car, and confirm each connector is plugged into the right sensor.
4. Check the exhaust for leaks near the sensor.
5. Check for heater code P0161 if present.

How to fix5

1. Repair the wiring or connector and secure it with its clips.
2. Correct the connections if they were swapped.
3. Repair any exhaust leak.
4. Replace the bank 2 downstream oxygen sensor if it is proven faulty.
5. Clear the codes and drive until the converter test completes.

A wiring or connector repair is cheap; a new sensor is what raises the cost, and labor may grow if the sensor is rusted in place.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions