P0137: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0137 means the engine computer is seeing too little voltage from the rear oxygen sensor on Bank 1, which is the sensor after the catalytic converter. The most common fix is replacing the faulty O2 sensor or repairing its wiring, typically costing about $150 to $400 at an independent shop.
- Severity
- Moderate
- Can I drive?
- Drive with caution
- DIY?
- Possible with some experience
- Repair cost range
- $100 – $500
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What does P0137 mean?
The Bank 1 Sensor 2 oxygen sensor monitors exhaust after it passes through the catalytic converter. The computer uses its signal to check catalyst performance and fine-tune fuel control under certain conditions. When the voltage stays too low, the PCM assumes the sensor circuit is not working correctly or the exhaust mixture data is not making sense. This code does not always mean the catalytic converter is bad; it often points to a sensor, wiring, or exhaust issue near the sensor.
Common symptoms
- Check engine light on
- Possible poor fuel economy
- May fail emissions test
- Rough running in some cases
- Other O2 or catalyst codes may be present
Causes, fixes and costs
P0137: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
General guide for most cars. Your car may differ.
The car will usually still drive, but the engine computer may not monitor emissions correctly and fuel economy can suffer. Stop driving if the engine starts running badly, misfiring, or if there is damage to the exhaust wiring or a strong exhaust leak.
Most likely causes
- 1
Faulty Bank 1 Sensor 2 oxygen sensorHigh
If the check engine light is on with no major drivability symptoms, a worn or contaminated rear O2 sensor is the most common cause. This is especially likely if the code returns after clearing and there are no obvious exhaust leaks.
Quick check: Inspect the sensor data with a scan tool; if the voltage stays near zero or switches very slowly, the sensor may be bad.
- 2
Damaged wiring or connectorHigh
Low voltage can happen if the sensor heater or signal wire is broken, melted, corroded, or loose. This is more likely if the code appeared after exhaust work, hitting road debris, or if the fault comes and goes.
Quick check: Look closely at the harness and plug near the rear sensor for melting, chafing, corrosion, or a loose connection.
- 3
Exhaust leak near the sensorMedium
A leak before or around the rear sensor can pull in outside air and skew the reading low. You may hear a ticking or hissing sound, especially during cold starts or acceleration.
Quick check: Listen for exhaust leaks and inspect the pipe, flex section, and sensor area for soot marks or leaking joints.
- 4
PCM or fuel mixture issueLow
If the sensor and wiring test good, a control issue or an engine running condition can sometimes trigger the code. This is less common and usually comes with additional codes or abnormal live data.
Quick check: Scan for related codes and compare Bank 1 Sensor 1, fuel trims, and sensor readings before replacing parts.
Can you fix it yourself?
Possible with some experience
Difficulty: Moderate. A handy owner can inspect the wiring and connector, but sensor replacement may need penetrating oil, a scan tool, and an oxygen-sensor socket. Ask the shop to diagnose the circuit, check for exhaust leaks, and verify the sensor signal before replacing the catalytic converter.
Show the stepsHide the steps
- Read all stored and pending codes
- Inspect the rear O2 sensor wiring and connector
- Check for exhaust leaks near the sensor
- Review live data for Bank 1 Sensor 2 voltage
- Replace the sensor if the circuit and exhaust are sound
- Clear the code and road test
- Recheck for returning codes
Estimated repair cost
$150 – $400
Replace Bank 1 Sensor 2 oxygen sensor: parts about $50-$150, labor about $100-$250
- Repair oxygen sensor wiring or connector$120 – $300
- Fix exhaust leak near rear sensor$120 – $500
- Diagnose engine management or PCM issue$100 – $200
Prices vary by vehicle, rust, sensor access, and local labor rates.
Frequently asked questions
Can I drive with P0137?
Usually yes for short trips, but get it checked soon. If the car starts running rough, loses power, or the exhaust is damaged, stop driving and have it towed.
Does P0137 mean my catalytic converter is bad?
Not usually. This code points to the rear oxygen sensor circuit or wiring first, and the converter is only suspected after the sensor and exhaust are checked.
Can I replace the oxygen sensor myself?
Yes, if the sensor is accessible and the threads are not rusted in place. You still need to inspect the wiring and clear the code afterward.
Will P0137 cause my car to fail inspection?
Very likely, because the check engine light is on and emissions monitors may not be ready. Fix the code before going to an emissions test.
What is Bank 1 Sensor 2?
Bank 1 is the side of the engine with cylinder 1, and Sensor 2 is the oxygen sensor after the catalytic converter. It helps the computer monitor emissions performance.
Related codes
- P0136 O2 Sensor Circuit (Bank 1 Sensor 2)
- P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
- P0420 Catalyst System Efficiency Below Threshold (Bank 1)
- P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)
- P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
- P0037 Ho2S Heater Control Circuit Low (Bank 1 Sensor 2)
Related problems
This guide covers most cars and is general advice, not an inspection. Prices are typical US independent-shop ranges and vary by region, car and shop. If your brakes, steering or a warning light feel unsafe, stop driving and contact a mechanic.