P0131 GMC Terrain
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1) · Powertrain Code · Medium · Repair: Moderate
What is P0131?
Low voltage from the upstream O2 sensor on bank 1, indicating a possible lean condition or sensor failure.
When the GMC Terrain triggers code P0131 (o2 sensor circuit low voltage (bank 1, sensor 1)), 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 upstream (Bank 1 Sensor 1) oxygen sensor
- Exhaust leak near the Bank 1 manifold or header
- Wiring damage or corrosion at the O2 sensor connector
- Lean fuel condition causing persistent low voltage on O2 sensor
Symptoms
- Check Engine Light on
- Poor fuel economy
- Rough idle
- Failed emissions test
- Engine may hesitate under load
Notes for GMC Terrain
GM V8 truck exhaust manifold bolts are known to break, causing exhaust leaks that trigger O2 sensor codes — check manifold bolt integrity before replacing the sensor.