P0137: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
TL;DR
P0137 = downstream O2 sensor low voltage (B1S2). Severity: low. Safe to drive; fails emissions. Top causes: worn O2 sensor (55%), wiring/connector (25%), exhaust leak (20%). Fix: $50–$250 DIY.
Can I keep driving with P0137?
IF you have P0137 → drive normally; the downstream sensor doesn’t control fueling, so performance is unaffected. The main consequence is failing emissions, so repair it before testing.
Symptoms
- Check engine light on
- Failed emissions test
- Little or no change in how the car drives
- Sometimes a slight economy effect
Top causes (ranked by probability)
| Likely cause | Probability | Notes |
|---|---|---|
| Worn / degraded downstream O2 sensor | 55% | Most common |
| Wiring or connector fault | 25% | |
| Exhaust leak near the sensor | 20% |
What does P0137 mean?
Technical explanation
The post-catalyst Bank 1 sensor signal stays low (lean-biased) outside its expected range. Since this sensor judges converter efficiency rather than controlling fueling, drivability is unaffected. Causes are a degraded sensor, a signal-wire/connector fault, or an exhaust leak near the sensor admitting air.
In simple terms
The oxygen sensor after the catalytic converter keeps reading low. The car runs fine, but it’ll fail emissions until fixed. Usually the sensor is worn out, or there’s a wiring problem or exhaust leak nearby.
How to diagnose P0137 (step by step)
- Confirm sensor location. Bank 1 Sensor 2 is the downstream sensor after the catalytic converter.
- Check for exhaust leaks. A leak near the rear sensor can skew it low.
- Inspect wiring/connector. Look for damage or a short near the exhaust.
- View live data. The downstream signal should be relatively steady; a stuck-low reading suggests a bad sensor.
- Replace the sensor. Fit an OEM-grade downstream O2 sensor if wiring and exhaust are good.
Repair options & cost
- Replace the downstream (B1S2) O2 sensor
- Repair wiring/connector
- Fix exhaust leaks near the sensor
| DIY cost | $50–$250 |
|---|---|
| Workshop cost | $150–$400 |
| Repair time | 30–60 min |
Costs are local ballpark ranges and vary by region and vehicle.
Tools you’ll need
- OBD-II scanner (BlueDriver / ANCEL)
- O2 sensor socket
- Multimeter
Vehicle-specific notes
- The downstream sensor is usually easier to reach than the upstream one.
- Rule out an exhaust leak first.
- Use an OEM-grade sensor for reliability.
Common mistakes to avoid
- Replacing the upstream sensor by mistake
- Ignoring an exhaust leak
- Using a cheap sensor
- Assuming it affects performance (it doesn’t)
Frequently asked questions
Is P0137 safe to drive with?
Yes. The downstream sensor monitors the converter, not fueling, so the car drives normally. You will fail emissions until it’s fixed.
What causes P0137?
Most often a worn downstream O2 sensor, then a wiring/connector fault or an exhaust leak near the sensor.
What is the difference between P0137 and P0141?
P0137 is a low-voltage signal fault on the downstream sensor; P0141 is specifically that sensor’s heater-circuit fault. Both are Bank 1, Sensor 2.
P0137 summary
| Meaning | Downstream O2 sensor low voltage (B1S2) |
|---|---|
| Severity | Low |
| Safe to drive? | Yes |
| Top cause | Worn O2 sensor (55%) |
| DIY cost | $50–$250 |
| Shop cost | $150–$400 |