P0137 often turns on the Check Engine Light without changing how the car drives. That can make the oxygen sensor look like an easy fix, but the same low reading can come from a wiring fault or exhaust problem. I check the signal and circuit before recommending a sensor.
What the P0137 code means
P0137 means the engine computer detected a low-voltage signal from the Bank 1 Sensor 2 oxygen-sensor circuit. Bank 1 is the side of the engine with cylinder 1. Sensor 2 is usually the downstream sensor, located after the catalytic converter. If you’re unsure which side is Bank 1, see our guide to Bank 1 vs. Bank 2.
A low signal can mean the sensor is detecting excess oxygen in the exhaust, or that an electrical problem is pulling the signal low. The vehicle’s sensor type and diagnostic strategy determine how the computer sets the code. P0137 does not prove that the sensor or catalytic converter has failed.
Symptoms of P0137
The Check Engine Light may be the only symptom. On many vehicles, the downstream sensor mainly monitors catalytic-converter performance, so the car may seem to run normally.
- Check Engine Light
- Failed emissions test
- Possible change in fuel economy or engine performance, depending on the vehicle and cause
Common causes of P0137
- Faulty downstream oxygen sensor: The sensor may be slow to respond or produce a signal that stays too low.
- Damaged wiring or connector: A short to ground, open circuit, corrosion, loose connection, or heat-damaged wire can affect the signal.
- Exhaust leak near the sensor: A leak close to the sensor can let outside air affect its reading.
- Lean-running engine: An engine problem that leaves excess oxygen in the exhaust may contribute to a low sensor reading. Check for related codes and fuel-trim data.
- Engine computer fault: This is uncommon. Check the sensor and circuit before suspecting the computer.
Can you drive with P0137?
If the Check Engine Light is steady and the engine runs normally, you can usually arrange a prompt repair without stopping immediately. Don’t ignore the code, since the emissions system may not be working as intended. If the engine is misfiring, losing power, or running poorly, diagnose those symptoms before driving far.
How to diagnose P0137
I first check whether the low signal is coming from the sensor’s reading or from an electrical problem. Sensor designs and test values vary, so I use the service procedure for the exact vehicle instead of applying one voltage rule to every car.
- Scan for all codes and save the freeze-frame data. Look for oxygen-sensor heater codes, fuel-trim codes, and other faults that may explain the low reading. Record the data before clearing anything.
- Confirm the sensor location. Verify that the affected sensor is Bank 1 Sensor 2 using the vehicle’s service information. Sensor locations vary by engine layout.
- Inspect the connector and wiring. Look for corrosion, loose pins, melted insulation, or wires touching the exhaust. Check the harness routing before replacing the sensor.
- Check for an exhaust leak near the sensor. Inspect the exhaust joints and sensor bung. Confirm a suspected leak with a suitable test rather than spraying flammable cleaner around a hot exhaust.
- Review live data under the correct conditions. Compare the downstream sensor reading with the manufacturer’s expected behavior. On some vehicles, the service procedure calls for a specific engine temperature or operating condition before the reading is meaningful.
- Test the circuit and sensor as specified. Check the signal wire for an open or short and verify any required power and ground. If the wiring is good, test the sensor using the vehicle-specific procedure. A multimeter or oscilloscope may be needed.
- Repair the confirmed fault and verify it. Clear the code after saving the original information, run the applicable monitor or drive cycle, and confirm P0137 does not return.
A compatible OBD2 scanner can show the sensor data and related codes. For exact pinouts and test conditions, use the service information for your vehicle.
Repairs that can fix P0137
The repair depends on what testing finds. Possible fixes include:
- Replacing a downstream oxygen sensor that fails its test
- Repairing damaged wiring or a connector
- Repairing an exhaust leak near the sensor
- Diagnosing and correcting an engine condition that is producing excess oxygen in the exhaust
A catalytic converter replacement is not a direct fix for P0137 unless testing identifies a separate converter problem. For more information, see our guide to oxygen sensor symptoms.
Oxygen sensor replacement cost
If testing confirms the oxygen sensor has failed, replacement averages about $440 to $523, according to RepairPal. That estimate is for sensor replacement, not diagnosis or every possible fix for P0137. In my experience, sensor location and access can affect labor, so ask for a quote based on your exact vehicle.
Frequently asked questions
Does P0137 mean the oxygen sensor is bad?
No. A faulty sensor is one possible cause, but wiring, an exhaust leak, or an engine condition can also produce a low signal. Test the circuit before replacing parts.
Which oxygen sensor is P0137?
P0137 usually refers to Bank 1 Sensor 2, the downstream oxygen sensor after the catalytic converter. Confirm the location using service information for your vehicle.
Can P0137 affect how the car runs?
Often the Check Engine Light is the only noticeable symptom, but the effect depends on the vehicle and the underlying fault. If the engine runs poorly, check for related codes and diagnose those symptoms as well.
