Powertrain, generic · Fuel and air metering

P0151 O2 Sensor Circuit Low Voltage Bank 2 Sensor 1

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The oxygen sensor before the catalytic converter on bank 2 (sensor 1) is the main control sensor for the mixture. It is either a switching sensor (about 0.1 V lean to 0.9 V rich) or a wide-band sensor that works with a pump current evaluated by an interface chip. Bank 2 exists only on engines with two exhaust manifolds. P0151 is the bank 2 counterpart of P0131. On switching sensors the signal stays below about 40–50 mV in closed loop with a stoichiometric target (GM LT4: 285 of 350 samples; GM 3.0/3.6 V6 within 50 s); on wide-band sensors the interface chip reports a sensor wire shorted to ground. Two trips. A genuinely lean bank 2 shows up as P0174 rather than this code. A stored code usually switches mixture control to open loop and suspends adaptation and converter monitoring.

Likely causes

Signal wire (or a wide-band sensor wire) shorted to ground, e.g. chafed on exhaust or gearbox
Sensor faulty or poisoned (permanently lean signal)
Large exhaust leak ahead of the sensor or misfires
Connector wet or corroded

Symptoms

  • Check engine light on
  • Higher consumption, possibly rough running (no mixture control)
  • Higher emissions, possible emissions test failure
  • Possibly with P0174/P2197

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–350
Time0.5–2.5 h

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

What to check first

  1. Look for exhaust leaks upstream of the sensor
  2. Check fuel trims
  3. Inspect wiring

Parts involved

oxygen sensor bank2 sensor1oxygen sensor wiringengine control module

Related codes

P0131P0150P0152P0154P0174P2197

References: law.cornell.edu, gsi.ext.gm.com, newtonnet.co.uk, saabwisonline.com.