P0137 Kia Forte
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 Kia Forte 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 Kia Forte.
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 Kia Forte.
Common Causes on Kia Forte
- Failed downstream O2 sensor (Bank 1 Sensor 2)
- Exhaust leak between catalytic converter and downstream sensor
- Contaminated sensor from coolant or oil in exhaust
- 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 Kia Forte
If P0137 appears with P0420, diagnose the catalyst first before replacing the downstream sensor.