P0157 OBD II Trouble Code 02 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

Detailed information on troubleshooting and repairing a P0157 DTC code which refers to a low voltage in the number 2 O2 sensor circuit on bank 2. Also includes links to relevant forum topics on the code.

Symptoms of P0157 OBD II Trouble Code

  • MIL (Malfunction Indicator Lamp) illumination
  • Engine performance issues
  • Engine running rough
  • Engine running rich (only if PCM is trying to add fuel to compensate for low o2 sensor voltage reading)
  • Engine running lean (only if vacuum leak is large enough that PCM can't compensate by adding fuel)
  • Poor idle

Common Causes of P0157 OBD II Trouble Code

  • Air leaks in exhaust in front of o2 sensor giving false reading
  • Engine running excessively lean
  • O2 sensor connector damaged/corroded
  • O2 sensor signal circuit is shorted to ground
  • O2 sensor ground circuit is open
  • O2 sensor has failed (it may be contaminated with fuel or coolant)
  • PCM has failed