P0165 — O2 Sensor Slow Response, Bank 2 Sensor 3

What P0165 means

The engine control module watches the signal from the Bank 2, Sensor 3 oxygen sensor and compares how fast it switches with what it expects. A healthy sensor swings quickly between rich and lean readings. When the signal changes too slowly, the module stores P0165 and turns on the check engine light. Which physical sensor is number 3 depends on the exhaust layout, so confirm its location for your vehicle.

Symptoms

• Check engine light on
• Slightly worse fuel economy
• Occasional rough idle or hesitation
• Higher exhaust emissions
• Often no other noticeable symptoms

Possible causes

1. Worn or contaminated Bank 2 Sensor 3 oxygen sensor
2. Damaged sensor wiring: open, short or corrosion
3. Poor connector contact or corrosion
4. Exhaust leak near the sensor
5. Failed sensor heater circuit
6. Mixture problem upstream (uncommon)
7. Engine computer fault or calibration issue (rare)

How to diagnose

1. Read all codes and freeze frame data; fix any misfire or fuel mixture codes first.
2. Find Bank 2, Sensor 3 on your vehicle using the service information.
3. Inspect the sensor harness and connector for chafing, heat damage, corrosion or moisture.
4. Check the exhaust near the sensor for leaks or a failed gasket.
5. Use a scan tool to watch the sensor signal and heater status live.
6. Review short and long term fuel trims for signs of a mixture problem.
7. Test the power, ground, heater and signal circuits with a multimeter per the wiring diagram.
8. If wiring and exhaust are fine, replace the sensor and clear the code.

Common fixes

• Replace the Bank 2 Sensor 3 oxygen sensor
• Repair the wiring or replace the connector
• Repair the exhaust leak
• Correct any mixture issue that is found
• Reprogram or replace the engine computer (very rare)

Questions and answers

Can I drive with a P0165 code?

Usually yes for a short time. It rarely harms the engine right away, but fuel use and emissions may rise, so get it diagnosed soon.

What most often causes P0165?

Most often it's an aging sensor or a wiring or connector problem. Rule out an exhaust leak before buying a new sensor.

Will P0165 go away on its own?

The light may go out if the fault doesn't recur over several drive cycles, but the cause is still there. It's better to find and fix it.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.