P0159 Code: O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)
🟠 Moderate severity · drivable
Drivable, but the sluggish sensor can lower fuel economy and cause an emissions test failure.
What P0159 means
The bank 2 sensor 2 oxygen sensor, which sits after the catalytic converter, is reacting too slowly to changes in exhaust oxygen. A healthy sensor switches its voltage quickly; a slow one drags behind. This is mostly an emissions and fuel economy concern.
Symptoms
- Check engine light is on
- Worse fuel economy
- Failed emissions test
- Usually no noticeable driving symptoms
Common causes
- most common: Aging or contaminated oxygen sensor
- common: Exhaust leak near the sensor
- less common: Wiring or connector problem
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the bank 2 sensor 2 oxygen sensor | Yes | $60–200 |
| Repair an exhaust leak near the sensor | Mechanic | $50–200 |
Frequently asked questions
Can I drive with a P0159 code?
Yes. It mainly affects emissions and fuel economy, not safety or drivability.
What does "slow response" mean?
The sensor takes too long to switch its voltage when exhaust oxygen changes, so the computer flags it as sluggish.
What is the most common cause of P0159?
An old or contaminated downstream oxygen sensor, sometimes worsened by an exhaust leak.
Related codes
P0156
P0156 Code: O2 Sensor Circuit Malfunction (Bank 2 Sensor 2)
P0160P0160 Code: O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)
P0139P0139 Code: O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.