P0159 code meaning
O2 Sensor Circuit Slow Response Bank 2 Sensor 2
Powertrain system Generic code P01xx codes Check engine light
What P0159 means
The oxygen sensor after the catalytic converter on bank 2 (sensor 2) is a switching sensor (about 0.1–0.9 V) used for converter monitoring and fine mixture trim. Bank 2 exists only on V and boxer engines with a separate downstream sensor per bank. P0159 means the downstream sensor on bank 2 reacts too slowly to mixture changes, typically measured around fuel cut-off. Thresholds are documented only for the bank 1 counterpart P0139 (Subaru: 0.51 s rich to lean, 2 s lean to rich); Jaguar Land Rover lists P0159 for its mid-cat sensor after water-induced thermal shock. Newer GM and Ford systems report direction-specific codes P013C/P013D and P014A/P014B instead. When it fails, the control module stops the downstream trim and cannot evaluate the converter; there is no limp mode.
P0159 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0159
- Check engine light on (usually after two drive cycles)
- Catalyst monitor readiness not set
- P0430 may follow
Common causes of P0159
- Most likelySensor aged or contaminated (oil ash, silicone, additives)
- PossibleExhaust leak ahead of the sensor
- PossibleSensor heater weak, sensor too cold
- Less likelyThermal shock damage from water
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor bank2 sensor2Oxygen sensor wiringCatalytic converter
What each part of P0159 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 59 | The exact fault in that area. |
What to do next
- Note P0159 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0159
What does P0159 mean?
P0159 means "O2 Sensor Circuit Slow Response Bank 2 Sensor 2". The oxygen sensor after the catalytic converter on bank 2 (sensor 2) is a switching sensor (about 0.1–0.9 V) used for converter monitoring and fine mixture trim. It is a generic code, so it means the same on every make.
Is it safe to drive with P0159?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0159 fail an emissions test?
Yes, it can. P0159 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0159 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0159 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.