Powertrain, generic · Fuel and air metering

P0159 O2 Sensor Circuit Slow Response Bank 2 Sensor 2

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Sensor aged or contaminated (oil ash, silicone, additives)
Exhaust leak ahead of the sensor
Sensor heater weak, sensor too cold
Thermal shock damage from water

Symptoms

  • Check engine light on (usually after two drive cycles)
  • Catalyst monitor readiness not set
  • P0430 may follow

Repair estimate

DifficultyEasyDIY possible
Parts and labour€60–250
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

oxygen sensor bank2 sensor2oxygen sensor wiringcatalytic converter

Related codes

P0139P0160P0157P0158P013CP0430

References: law.cornell.edu, static.nhtsa.gov, saabwisonline.com.