P0137
Low SeverityO2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
Emissions System
P0137 — Instant Answer
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
Severity: LOW SEVERITY
Meaning: Downstream O2 sensor on bank 1 is reading too low. Could indicate a failing sensor or a lean exhaust condition.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $25 - $80
Most common causes:
- 1. Failed downstream O2 sensor (35-45% of cases)
- 2. Exhaust leak after cat (10-25% of cases)
- 3. Deteriorating catalytic converter (10-25% of cases)
Symptoms
- ⚠️Check engine light
- ⚠️Failed emissions test
- ⚠️Possible P0420 code
Related Symptoms
Common Causes
How to Diagnose P0137
- 1Check for exhaust leaks after catalytic converter
- 2Monitor sensor voltage
- 3Compare upstream and downstream readings
- 4Replace sensor if stuck low
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Related Symptoms
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Related Codes
General fault with the downstream (post-cat) O2 sensor on bank 1. This sensor monitors catalytic converter efficiency.
Downstream O2 sensor bank 1 is stuck at a high voltage. Usually a failed sensor.
The catalytic converter on bank 1 is not converting pollutants efficiently. This is one of the most common DTCs.
Frequently Asked Questions
- 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.
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Author & Review
Written by AllOEMManuals Editorial Team. Reviewed by ASE-certified technicians and updated with factory-reference checks for fitment-sensitive steps.
This guide was drafted with AI assistance and reviewed for accuracy by a human editor.
Last updated: 2026-05-07