O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
The P0137 code indicates that the oxygen sensor located after the catalytic converter (sensor 2) on bank 1 is reporting a voltage below the normal operating range (typically below 0.1 volts). This sensor monitors the oxygen content in the exhaust to evaluate catalytic converter efficiency. A low voltage condition can be caused by a faulty sensor, wiring issues, exhaust leaks, or a rich fuel mixture. If left unresolved, it may lead to increased emissions, poor fuel economy, and potential damage to the catalytic converter.
1. Most Common Causes
- Faulty or worn rear oxygen sensor (Bank 1, Sensor 2)
- Sensor wiring shorted to ground or has excessive resistance
- Corroded, oxidized, or damaged connector pins at the sensor
- Exhaust leak near the sensor (e.g., manifold or pipe leak introducing false air)
- Clogged or inefficient catalytic converter affecting sensor readings
- Rare internal ECM/PCM failure
- Contaminated fuel or improper additives damaging the sensor
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Poor fuel economy
- Rough idle or hesitation
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect O2 sensor wiring and connector for damage or corrosion.
Step 3: Using a multimeter, check sensor signal voltage at idle (should fluctuate between 0.1-0.9V). If stuck below 0.1V, suspect sensor or wiring.
Step 4: Check for exhaust leaks upstream of sensor 2 using a smoke machine or soapy water.
Step 5: If wiring and exhaust are okay, replace the oxygen sensor.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances, but it may cause poor fuel economy and increased emissions. Prolonged driving could damage the catalytic converter.
How much does it cost to fix?▼
Typically $50-$150 for a DIY sensor replacement; labor at a shop adds $50-$100.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.