P0159 — O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)
Drive with caution — fix soon.
What P0159 means
This code means the downstream oxygen sensor on bank 2 is switching between rich and lean too slowly, so the computer can't reliably evaluate the catalytic converter. It's most often caused by an aging or contaminated rear sensor, though wiring problems or an exhaust leak can contribute. The usual fix is replacing the sensor, and it rarely requires major engine work.
Common symptoms
- Check engine light is on
- Often little change in how the car drives
- Slight reduction in fuel economy
- Failed emissions or readiness test
- Occasional hesitation in rare cases
Common causes
- Aging or contaminated downstream O2 sensor on bank 2
- Carbon or oil deposits on the sensor tip
- Corroded or damaged sensor wiring or connector
- Exhaust leak near the rear sensor
- Internal degradation of the sensor element
Typical repair cost
$150 – $350
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0159 code?
Usually yes, for a short time. The car typically drives normally since this is the rear emissions-monitoring sensor. Have it checked within a week or two and before any emissions test.
How much does it cost to fix a P0159 code?
Most repairs run $150 to $350. The downstream oxygen sensor and labor are the main costs, while a wiring or exhaust fix can be on the lower end.
Is a P0159 code serious?
It's a moderate concern. It usually doesn't affect drivability, but the slow sensor makes it harder to monitor the catalytic converter and will cause an emissions test failure if ignored.
What's the difference between P0159 and P0160?
Both involve the bank 2 sensor 2 circuit. P0159 flags a slow-responding sensor, while P0160 indicates the sensor shows no activity at all. They often point to the same sensor wearing out, just at different stages.