O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)
The P0159 code means the vehicle's onboard diagnostic system has detected: O2 Sensor Circuit Slow Response (Bank 2 Sensor 2). This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $80 - $300 (O2 sensor $60-$200; labor $50-$150)
Test O2 sensor voltage (should fluctuate 0.1-0.9V). Do not replace a $150 sensor without confirming it is actually bad first.
Shows real-time O2 sensor readings on your phone. See if the sensor is lazy, stuck, or actually working before spending money.
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Common Symptoms
- Check Engine Light on
- No significant drivability symptoms
- Slightly increased emissions
- Catalyst monitor readiness may not complete
- Possible emissions test failure
Probable Causes (Ranked by Likelihood)
- Aging downstream O2 sensor with degraded response Very High
- Contaminated sensor element High
- Exhaust leak near the sensor location Moderate
- High resistance in signal wiring Moderate
- Deteriorating catalytic converter on bank 2 Low
Frequently Asked Questions
Can I drive with code P0159?
Yes, you can drive normally. A slow downstream sensor does not affect engine performance or fuel control. The only consequences are increased emissions and a Check Engine Light.
Is P0159 the bank 2 version of P0139?
Yes. P0139 is the slow response code for bank 1 sensor 2, and P0159 is the same fault on bank 2 sensor 2.
Should I replace the catalytic converter for P0159?
No, start with the O2 sensor. P0159 most commonly indicates a worn sensor, not a catalyst problem. Only evaluate the catalytic converter if the code returns after sensor replacement.
What actually makes the computer set an oxygen sensor code?
The OBD II regulation requires four separate detections for an oxygen sensor (Title 13 CCR 1968.2, section (e)(7.2)): deterioration in voltage, response rate or amplitude that would push emissions past 1.5 times the FTP standards; loss of circuit continuity; out-of-range values; and the case where the sensor has degraded enough that the fuel system stops using it and falls back to open loop. A sensor can therefore set a code while still producing a signal that looks plausible on a scan tool. This is the threshold the monitor is designed around, not a description of your specific fault — the regulation says what the system must detect, not how to find it on your vehicle.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Monitor bank 2 sensor 2 response on a scan tool during steady-state driving. The sensor should respond to exhaust changes. Very slow transitions indicate a lazy sensor.
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Compare the response rate to the bank 1 downstream sensor. Significantly different rates point to a sensor issue on the slower bank.
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Check for exhaust leaks near the sensor that could dilute the exhaust and slow response.
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Inspect the sensor for contamination or physical damage.
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Measure signal wire resistance to rule out wiring issues.
Sources 3
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1968.2 (OBD II)malfunction criteria, section (e)
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- 2007-2016 Toyota Tundra (5.7L V8)
- 2005-2014 Nissan Pathfinder (4.0L V6)
- 2008-2016 Honda Pilot (3.5L V6)
- 2009-2017 Ford F-150 (5.0L V8)
- 2010-2018 Chevrolet Silverado (5.3L V8)
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