Can P0137 mean the catalytic converter is bad?

Not usually — P0137 is more likely the sensor itself. P0420 is the code that indicates catalytic converter efficiency issues.

Should I replace both O2 sensors?

Not necessarily. Only replace the one that has failed. However, if both are original and high-mileage, replacing both saves labor.

Low Severity

Emissions System

Downstream O2 sensor on bank 1 is reading too low. Could indicate a failing sensor or a lean exhaust condition.

Common Fix

Replace downstream O2 sensor

Estimated Cost (DIY)

$25 - $80

Failed downstream O2 sensorlikely

Exhaust leak after catpossible

Deteriorating catalytic converterpossible

Need to read or clear this code?

Ready to fix it yourself?

Select your exact vehicle for a personalized guide

Can P0137 mean the catalytic converter is bad?: Not usually — P0137 is more likely the sensor itself. P0420 is the code that indicates catalytic converter efficiency issues.
Should I replace both O2 sensors?: Not necessarily. Only replace the one that has failed. However, if both are original and high-mileage, replacing both saves labor.

Need a diagnosis for your specific vehicle?

100% Free — No signup required