P0159 means O2 Sensor Circuit Slow Response (Bank 2 Sensor 2). The downstream oxygen sensor on bank 2 is responding too slowly when the fuel mixture changes. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0159 means
Oxygen sensors measure the oxygen left in the exhaust. Sensor 1 sits before the catalytic converter and is used for fuel control; sensor 2 sits after it and mainly monitors the converter. Most sensors have a heater so they start working soon after a cold start. A traditional zirconia sensor switches between about 0.1 volt (lean) and 0.9 volt (rich); many newer upstream sensors are wide-band air-fuel sensors that report differently, so check which type your engine uses.
P0159 symptoms
- Check engine light
- Usually no drivability change
Common causes of P0159
- Aging or contaminated sensor
- Exhaust leak near the sensor
- Heater circuit fault
How to diagnose P0159
- Check sensor response on a scan tool
- Check the heater circuit
- Check for exhaust leaks
Can you drive with P0159?
Usually yes for a while, but fix it to protect fuel economy and the catalytic converter.
P0159 tips
Fix any exhaust leak ahead of the sensor first; outside air entering the exhaust changes its readings.
Will P0159 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0159 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0157 | O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2) |
| P0158 | O2 Sensor Circuit High Voltage (Bank 2 Sensor 2) |
| P0161 | O2 Sensor Heater Circuit (Bank 2 Sensor 2) |
Guides that help
When it is more than a sensor
Oxygen sensor codes are fixed with a sensor, wiring, a fuse or an exhaust leak repair. An engine burning oil or coolant contaminates sensors quickly; if new sensors keep failing, check for blue or white exhaust smoke and a head gasket leak, and compare engines by code on our engines page if the engine is worn out.
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