P0165: O2 Sensor Circuit Slow Response Bank 2 Sensor 3

What does P0165 mean?

Sensor 3 on bank 2 is a switching oxygen sensor behind a second converter or converter brick. It is rare – documented for Jaguar Land Rover's supercharged V6 and V8 (2013–2016), where it is the 'post-cat' sensor of the second bank, and for Ford systems that monitor part of the converter volume. P0165 means sensor 3 reacts too slowly to mixture changes, typically measured around fuel cut-off as for the downstream sensor 2 (Subaru limits for P0139: 0.51 s rich to lean, 2 s lean to rich). No manufacturer document using exactly this code was found – the Jaguar Land Rover bulletins list only P0162–P0164 and P0167 for this sensor. The description rests on CARB's response requirement for downstream sensors and the sensor 2 logic. When it fails, the downstream evaluation of that converter is suspended; there is no limp mode.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on (usually after two drive cycles)
• Catalyst readiness incomplete
• Usually no noticeable change in driving

Common causes

• High Sensor aged or contaminated
• Medium Sensor heater weak
• Medium Exhaust leak ahead of the sensor
• Low Wiring or connector high-resistance

Likelihood is a general estimate across vehicles; your make and model may differ.