OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P0151

O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)

Same condition as P0131 but on bank 2. The upstream sensor sees a continuously lean exhaust on bank 2 or has a signal short to ground.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number1 / 51

Possible causes

  • Exhaust leak upstream of the sensor high
  • Bank 2 running lean (vacuum leak, fuel pressure) medium
  • Connector pins corroded - high contact resistance low

Symptoms

  • Check engine light on
  • Increased fuel consumption
  • Possible rough idle or hesitation
  • Failed emissions test

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 60–400 €
  • Estimated time: 0.5–3 h
  • Component: oxygen sensor upstream
  • Component: exhaust pipe pre cat
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication