O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
The P0137 code indicates that the oxygen sensor located after the catalytic converter (downstream) on Bank 1 is reporting a voltage lower than the expected range (typically below 0.1 volts). This sensor monitors the catalytic converter's efficiency by measuring oxygen content in the exhaust. A low voltage reading suggests the sensor is stuck lean, indicating either a faulty sensor, an exhaust leak, or a rich fuel condition causing the sensor to malfunction. This can lead to increased emissions and reduced fuel economy.
01. Most Common Causes
- Faulty oxygen sensor (Bank 1 Sensor 2)
- Exhaust leak before the sensor
- Wiring or connector issues (shorted, corroded, or open circuit)
- Engine vacuum leak causing lean condition
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Decreased fuel economy
- Possible rough idle or hesitation
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the O2 sensor wiring and connector for damage or corrosion.
Step 3: Check for exhaust leaks near the sensor using a smoke machine or soapy water.
Step 4: Using a multimeter, measure the sensor's voltage output at idle and while revving; should fluctuate between 0.1-0.9V.
Step 5: If voltage stays low, replace the downstream O2 sensor (Bank 1 Sensor 2).
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause reduced fuel economy and increased emissions. It's best to diagnose and repair promptly to avoid failing an emissions test.
How much does it cost to fix?▼
Typically $150-$300 including parts and labor. The sensor itself costs $50-$150, and labor is about $50-$150.