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P0159: O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)
Severity: Low With a steady light and normal running, arrange diagnosis soon. Stop for a flashing light, severe misfire, overheating, or a glowing catalyst; do not assume those symptoms are only a sensor fault.
What does P0159 mean?
The downstream bank 2 oxygen sensor responds too slowly during a defined test. Slow rear-sensor movement can be normal outside that test, so the code needs confirmation under the correct warm-up and operating conditions.
Generic OBD-II definition: O2 Sensor Circuit Slow Response (Bank 2 Sensor 2). Confirm applicability in your vehicle service information.
Common causes
- Aging bank 2 rear sensor
- Frayed sensor cable or poor contact
- Exhaust leak affecting the response test
Symptoms
- Steady check engine light
- Usually no clear drivability change
- Failed emissions monitor
Diagnostic focus
Do not compare a cold bank 2 rear sensor to a hot bank 1 sensor and call the difference a failure. Verify both are at operating temperature before comparing their behavior.
Can I keep driving with P0159?
Severity: Low With a steady light and normal running, arrange diagnosis soon. Stop for a flashing light, severe misfire, overheating, or a glowing catalyst; do not assume those symptoms are only a sensor fault.
If the check engine light is flashing or the car runs badly, stop driving and have it checked.
Typical fixes
- Inspect bank 2 exhaust sealing and rear wiring
- Resolve heater faults first
- Run the specified downstream response monitor after repairs
Related codes
O2 Sensor Circuit Malfunction (Bank 2 Sensor 2)P0160
O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)P0161
O2 Sensor Heater Circuit (Bank 2 Sensor 2)P0139
O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
Sources & review
Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.