OBD-II Code · Sensors
P0159
O2 Sensor Slow Response (B2S2)
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$150–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Bank 2 downstream slow response.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Likely causes
- Aging sensor
Read the full diagnostic procedureP0159 means the bank 2, sensor 2 O2 sensor is responding too slowly — exactly the bank-2 mirror of P0153/P0133 family slow-response codes.
P0159 means the bank 2, sensor 2 O2 sensor is responding too slowly — exactly the bank-2 mirror of P0153/P0133 family slow-response codes. Bank 2 sensor 2 lives on the post-cat side of bank 2 (the cylinder bank that does NOT contain cylinder 1 on a V6/V8/V10/V12), and its job is catalyst monitoring rather than closed-loop fuel control. A healthy narrow-band post-cat sensor should hold steady around 0.6-0.8V with under 0.1V of swing per minute when the cat is functioning; transition speed under snap-throttle should be under 100-300 ms. The ECM throws P0159 when the sensor takes longer than the manufacturer's threshold (often 400-800 ms) to complete a lean-rich or rich-lean transition during the cat monitor sweep.
Cheapest-first ladder
- Scan live data and watch B2S2 transition time during a warm-engine snap-throttle — over 600 ms transitions are failed.
- Pull the sensor and inspect the tip for contamination — white silicone powder (bad RTV upstream), brown oil glaze (oil-burning engine), or yellow-gray sulfur ash (cheap fuel) all slow response.
- Check bank 2 fuel trims — if LTFT on bank 2 is over plus or minus 10%, the slow response is a downstream symptom of an upstream fuel/air problem; fix that first.
- If trims are clean and contamination is absent, replace the sensor. The expensive misdiagnosis is replacing the bank 2 catalyst ($1,200-$3,000) when the real fault is a $180 sensor — always confirm the sensor speed before condemning the cat.
Vehicle-specific patterns2007-2013 Toyota Tundra/Sequoia 5.7L 3UR-FE V8 sees P0159 commonly from sulfur fouling on bank 2 (the passenger-side bank, opposite cylinder 1) — Toy…
- 2007-2013Toyota Tundra/Sequoia 5.7L 3UR-FE V8 sees P0159 commonly from sulfur fouling on bank 2 (the passenger-side bank, opposite cylinder 1) — Toyota notes a tankful of premium fuel plus a 30-minute highway drive often clears the code without sensor replacement.
- 2009-2014Ford F-150 5.0L Coyote V8 throws P0159 from oil consumption through the PCV system fouling the bank 2 post-cat sensor after 100k miles.
- 2010-2018RAM 1500 5.7L Hemi with MDS sees P0159 from cylinder-deactivation residue glazing the bank 2 sensor element — the deactivated cylinders 5 and 8 sit on bank 2 on the Hemi layout.
- 2006-2012Mercedes-Benz GL450/ML550/E550 with the M273 5.5L V8 sees P0159 on bank 2 sensor 2 from a degraded sensor element around 100-130k miles, tracking with the balance-shaft wear pattern.
- 2007-2013BMW N62/N63 V8 (550i, 750i, X5 4.8i, X5 5.0i) throws P0159 from a failed sensor on the bank 2 (passenger-side) post-cat after extended heat-soak cycles.
Estimated repair$130 to $620.
Look up another code
P0159 — frequently asked
What does a P0159 code mean?
Bank 2 downstream slow response.
What causes a P0159 code?
Common causes: Aging sensor.
What are the symptoms of a P0159 code?
Typical symptoms: Check engine light.
Is it safe to drive with a P0159 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $150-$400.
How do I diagnose a P0159 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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