P0137: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
Updated November 12, 2026
The oxygen sensor after the catalytic converter on bank 1 is reading low voltage for too long. Low voltage normally means lean exhaust, so the computer either sees a real leak or a bad sensor signal.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A failed downstream oxygen sensor
- An exhaust leak between the converter and the sensor
- A signal wire shorted to ground
- A failed sensor heater, so it never warms up
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Check engine light
- Usually no change in how the car drives
- Possible failed emissions inspection
Is it safe to drive?
Safe to drive for now in most cases, but get it fixed so emissions monitors can complete.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Listen and look for exhaust leaks near the downstream sensor (with the exhaust cool before touching anything).
- Watch sensor 2 in live data. It should sit fairly steady, often around 0.5 to 0.8 volts, when the converter is warm and working; one stuck near 0 volts suggests the sensor, wiring or a leak.
- Check for heater code P0141 and inspect the wiring under the car.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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Questions
What does P0137 mean?
P0137 is the generic OBD2 code for "O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)." The oxygen sensor after the catalytic converter on bank 1 is reading low voltage for too long. Low voltage normally means lean exhaust, so the computer either sees a real leak or a bad sensor signal.
Is it safe to drive with P0137?
Safe to drive for now in most cases, but get it fixed so emissions monitors can complete.
How do I check P0137 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Listen and look for exhaust leaks near the downstream sensor (with the exhaust cool before touching anything). Watch sensor 2 in live data. It should sit fairly steady, often around 0.5 to 0.8 volts, when the converter is warm and working; one stuck near 0 volts suggests the sensor, wiring or a leak. Check for heater code P0141 and inspect the wiring under the car.
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