P0137 GMC Terrain
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) · Powertrain Code · Medium · Repair: Moderate
What is P0137?
Low voltage from the downstream O2 sensor on bank 1.
When the GMC Terrain 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 GMC Terrain.
This repair is rated moderate, meaning some experience and specialty tools required.
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 GMC Terrain.
Common Causes on GMC Terrain
- Failed downstream (Bank 1 Sensor 2) oxygen sensor
- Exhaust leak between catalytic converter and downstream sensor
- Wiring damage to the post-cat O2 sensor
- Degraded catalytic converter causing abnormal downstream readings
Symptoms
- Check Engine Light on
- May be accompanied by P0420 (catalyst efficiency code)
- Slight decrease in fuel economy
- Failed emissions test
Notes for GMC Terrain
If P0137 appears alongside P0420, the catalytic converter is likely the root cause — replacing the downstream O2 sensor alone will not resolve it.