P0137 Hyundai Elantra
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 Hyundai Elantra 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 Hyundai Elantra.
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 Hyundai Elantra.
Common Causes on Hyundai Elantra
- Failed downstream O2 sensor (Bank 1 Sensor 2) past service life
- Exhaust leak between catalytic converter and downstream sensor
- Contaminated sensor from coolant leak into exhaust (head gasket issue on Theta II)
- Wiring damage to downstream O2 sensor
Symptoms
- Check Engine Light on
- Slightly worse fuel economy
- May set P0420 concurrently if catalyst is degraded
- Failed emissions test
Notes for Hyundai Elantra
If P0137 appears with P0420, diagnose the catalyst first; a bad converter can damage the downstream sensor readings.