P0137 Subaru Outback
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) · Powertrain Code · Medium · Repair: Easy
What is P0137?
Low voltage from the downstream O2 sensor on bank 1.
When the Subaru Outback triggers code P0137 (o2 sensor circuit low voltage (bank 1, sensor 2)), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Subaru Outback.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Subaru Outback.
Common Causes on Subaru Outback
- Failed rear O2 sensor (Bank 1 Sensor 2)
- Exhaust leak between catalytic converter and rear sensor
- Sensor contamination from coolant (head gasket issue) or oil
- Rear O2 sensor wiring damage from road debris
Symptoms
- Check Engine Light on
- Slightly worse fuel economy
- May set P0420 if converter is also degraded
- Failed emissions test
Notes for Subaru Outback
If P0137 accompanies P0420, diagnose the catalytic converter efficiency first before replacing the downstream sensor.