981 · Exhaust

P0157

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

LOW SEVERITY

Downstream Bank 2 sensor voltage stuck low.

SYMPTOMS

  • Check-engine light
  • Drivability or performance issues

LIKELY CAUSES

  • Faulty O2 sensor
  • Short to ground in the signal wire
  • Open ground or corroded connector
  • ECM/PCM fault (rare)

DIAGNOSIS STEPS

  • Inspect the O2 sensor wiring and connector
  • Check the signal circuit for a short to ground
  • Verify reference voltage and ground
  • Compare live data to expected
  • Replace the component if confirmed faulty

RELATED PARTS

  • Downstream O2 sensor (Bank 2)
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