You can usually drive for short periods, but you should diagnose and fix the issue soon. A P0137 code means the Bank 1 Sensor 2 oxygen sensor circuit is reporting a consistently low voltage.
In more detail, this downstream O2 sensor (the one after the catalytic converter) helps the engine computer monitor catalytic efficiency. A persistently low voltage can be caused by a faulty sensor, damaged wiring, or an exhaust leak, and it can affect emissions monitoring even if the engine seems to run normally.
What P0137 means
Bank 1 Sensor 2 is the downstream oxygen sensor. It normally reads voltage in a mid-to-high range as the exhaust passes through the catalytic converter; a reading persistently below about 0.2 volts typically triggers P0137. This signals a potential issue with the sensor circuit, the sensor itself, wiring, or an upstream exhaust condition that skews readings. While the engine’s driveability may not be dramatically affected, the vehicle’s emissions monitoring and cat-efficiency verification can be compromised.
Common causes of P0137 include:
- Faulty downstream O2 sensor (Bank 1 Sensor 2)
- Damaged, frayed, or corroded wiring or a loose/dirty connector for the downstream sensor
- Exhaust leak before the downstream sensor that skews readings
If this code appears by itself, you may still drive, but you should schedule service to confirm the cause and fix it. If additional codes accompany P0137, address those issues as well.
Symptoms you might notice
Not all vehicles show obvious symptoms, but potential indicators include:
- Check Engine/Service Engine Soon light on
- Minimal or no noticeable driveability issues, though fuel economy or emissions readiness may be affected
- Possible emission-test failure if the vehicle is tested
- Occasional exhaust odor or slight performance changes in some cars
Because symptoms vary by vehicle and by what else is happening under the hood, a diagnostic scan is the most reliable way to confirm the cause.
Is it safe to drive with P0137?
In most cases, you can continue driving in the short term, but proceed with caution. The code is not typically an immediate safety hazard, but it can prevent proper catalytic monitoring and raise emissions-related concerns. If you notice signs of a malfunction beyond the code (rough idle, stalling, power loss, or a flashing MIL), pull over and seek professional assistance.
Before embarking on long trips, plan to have the vehicle inspected and repaired to avoid potential emissions failures or downstream catalytic issues.
Diagnosis and potential fixes
Below are common diagnostic steps technicians follow to confirm and fix P0137. The order may vary by vehicle and shop.
- Inspect the downstream O2 sensor (Bank 1 Sensor 2) and its wiring for damage, corrosion, and secure connections
- Check for exhaust leaks upstream or near the sensor that could alter readings
- Use a scan tool to view live data from Bank 1 Sensor 2 and compare readings to expected behavior
- If the sensor voltage remains low and wiring checks out, replace the downstream O2 sensor
- Clear codes and test drive to confirm the code does not return
Concluding, replacing a faulty downstream O2 sensor or repairing a damaged harness often resolves P0137. If the problem persists after replacement, further diagnostics of the catalytic converter or ECU may be required.
Test methods you or a shop may perform
These tests help verify the issue and avoid unnecessary parts replacement:
- Live data monitoring of Bank 1 Sensor 2 voltage to confirm it stays consistently low
- Continuity and resistance checks on sensor wiring and connectors
- Visual inspection for exhaust leaks around the sensor location
- Functional testing of the sensor by substitution with a known-good unit
If you’re not comfortable with automotive diagnostics, consult a qualified technician for an accurate diagnosis and safe repairs.
Summary
A P0137 code signals a low-voltage reading from the downstream oxygen sensor (Bank 1 Sensor 2), which can affect emissions monitoring and catalytic efficiency without necessarily harming driveability immediately. You can drive for a short period, but plan to diagnose and repair the sensor, wiring, or exhaust condition to prevent emissions issues and potential catalytic damage. A professional diagnosis typically confirms whether the fix is a sensor replacement, wiring repair, or addressing an exhaust leak.