P0159 - O2 Sensor Circuit Slow Response (Bank 2, Sensor 2)

Bank 2 downstream oxygen sensor is switching too slowly.

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Code Overview

Bank 2 downstream oxygen sensor is switching too slowly.

Common Causes

• Aging downstream oxygen sensor on bank 2 sensor 2
• Exhaust leak affecting downstream sensor readings
• Catalyst efficiency problem on bank 2
• Rich or lean running condition affecting the monitor

Symptoms

• Check-engine light with little or no drivability change
• Failed emissions readiness or inspection
• Catalyst monitor may not complete normally

Diagnostic Steps

1. Watch bank 2 sensor 2 response on a scan tool after the engine is fully warm
2. Check for exhaust leaks ahead of the downstream sensor
3. Look for companion fuel-trim, misfire, or catalyst codes first
4. Compare downstream sensor behavior to catalyst and fueling conditions before replacing parts

Repair Difficulty

Moderate

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Likely Repairs & Cost Guides

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Related OBD Codes

Browse nearby code-family pages when the same fault pattern overlaps across systems, such as misfire, lean fuel trim, EVAP sealing, cooling, or charging faults.

Next Steps

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