P0137 — 02 Sensor Circuit Low Voltage (Bank I Sensor 2)

OBD2 code P0137 flags a problem with the sensor and actuator circuits (02 sensor circuit low voltage (bank i sensor 2)). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, blown fuse feeding the circuit, open or shorted wiring in the circuit.

powertrain (engine/transmission)

Is it safe to drive?

Usually drivable, but diagnose promptly P0137 can often be driven while monitoring the check-engine light, but continued operation may increase fuel consumption and allow incorrect fueling to damage the catalytic converter. Stop driving if the engine is severely rough, losing power, or the check-engine light is flashing.

Typical symptoms

The check-engine light illuminates and P0137 is stored in the powertrain control module
Rough idle, hesitation, or uneven acceleration may occur while the engine compensates for the low sensor signal
Fuel consumption may increase because the engine is operating on an incorrect air-fuel mixture
A sulfur or rotten-egg odor may be present if the engine is running rich
Additional fuel-trim or catalytic-converter codes may be stored when P0137 remains active

Common causes

A failed Bank 1 Sensor 2 oxygen sensor, normally located downstream of the catalytic converter
A short to ground or damaged signal wire in the oxygen-sensor harness
A corroded, loose, heat-damaged, or water-contaminated oxygen-sensor connector
An open circuit or high resistance in the sensor signal, ground, or reference connection
A defective oxygen-sensor heater circuit, including a blown fuse, fusible link, or poor heater ground
An exhaust leak upstream of Bank 1 Sensor 2 allowing incorrect exhaust gas to reach the sensor

How to diagnose with an OBD scanner

Read P0137 with an OBD2 scanner Connect an OBD2 scanner such as ELM327 or AIScanAuto, confirm P0137, and review freeze-frame data. Monitor Bank 1 Sensor 2 voltage and fuel-trim values; a signal that remains abnormally low or near zero indicates the fault more clearly than a stored code alone.
Locate the correct oxygen sensor Use the vehicle identification number or service-manual location diagram to identify Bank 1 Sensor 2. It is commonly the downstream oxygen sensor on the Bank 1 side of the engine, but the exact position must be verified before testing.
Inspect the sensor and wiring Check the sensor body, connector, wiring branches, and routing near the exhaust for corrosion, cracked insulation, heat damage, or water intrusion. Also inspect the exhaust pipe between the sensor and catalytic converter for leaks.
Perform electrical tests Back-probe the oxygen-sensor connector and compare signal voltage, ground continuity, and heater supply with service-manual specifications. Wiggle the harness during testing to reveal an intermittent open or short that can trigger P0137.
Repair and verification road test Repair the wiring or connector, replace the oxygen sensor or heater component as testing dictates, clear the codes, and road-test the vehicle. Confirm that P0137 does not return and that Bank 1 Sensor 2 voltage begins cycling correctly once the sensor reaches operating temperature.

Approximate repair cost

A typical independent-shop estimate for P0137 diagnosis and repair is USD $180-$650. This range includes connector or wiring repairs at the lower end and oxygen-sensor replacement with labor at the higher end. Figures are estimates and vary by region.

Common questions

Does P0137 always mean the oxygen sensor is defective?

No. P0137 can be caused by a failed Bank 1 Sensor 2 oxygen sensor, but a shorted wire, poor connector, defective heater circuit, or exhaust leak can produce the same low-voltage condition.

Can I continue driving with P0137 stored?

Usually yes, provided the engine runs normally and the check-engine light is steady. Arrange prompt diagnosis because an incorrect mixture can raise fuel consumption and contribute to catalytic-converter damage.

Where is Bank 1 Sensor 2 on my engine?

Bank 1 Sensor 2 is commonly the oxygen sensor downstream of the catalytic converter on the Bank 1 side. Verify its location with the VIN or wiring diagram before replacing any sensor.

Do I need to replace the catalytic converter for P0137?

Usually not. Test the sensor, connector, wiring, heater supply, and exhaust first; catalytic-converter replacement is considered only if separate catalyst-diagnosis tests confirm that the converter is damaged.

When the engine control unit detects that the downstream oxygen sensor on Bank 1 is producing an unusually low voltage signal, it stores trouble code P0137. This code belongs to the powertrain family and indicates the sensor is either failing to generate a proper voltage or the circuit feeding it has a problem preventing normal operation. Bank 1 refers to the cylinder bank containing cylinder number one, while Sensor 2 denotes the second sensor in the exhaust stream—the one located after the catalytic converter.

The control unit continuously monitors the oxygen sensor circuit by comparing live electrical readings against factory-calibrated thresholds. When these readings stay outside acceptable ranges for more than one complete drive cycle, the module logs P0137 and captures a freeze frame snapshot. That snapshot records engine RPM, load percentage, coolant temperature, and vehicle speed at the exact moment the fault occurred. Technicians use this data to recreate the driving conditions that triggered the code, making diagnosis faster and more accurate.

Beyond the stored code itself, the ECU may also activate a secondary air injection system or adjust fuel delivery strategy as a compensatory measure. Depending on your vehicle's programming, this can result in noticeable drivability changes even before any physical symptoms appear.

Common Symptoms

Illuminated Check Engine lamp
Limp-home mode engagement on some vehicles
Erratic or complete loss of the affected sensor's output
Noticeably higher fuel consumption compared to normal operation
Rough idle or hesitation during acceleration
Possible failure of emissions-related secondary systems

Likely Causes

Damaged, corroded, or loose electrical connectors in the sensor circuit
Wiring insulation chafing, melting, or rodent damage causing shorts or open circuits
Blown fuse supplying power to the oxygen sensor heater or signal circuit
Faulty oxygen sensor or related actuator component
Inadequate ground connection at the sensor or ECU
Control module internal driver failure affecting the sensor circuit

How to Diagnose P0137

Connect an OBD2 scanner and verify P0137 is present. Record all available freeze frame data before clearing anything—this information identifies the engine conditions present when the fault first appeared.
Scan for additional trouble codes. Related sensor codes often point toward the actual root cause rather than assuming the oxygen sensor itself has failed. Also search manufacturer technical service bulletins for your specific make, model, and year—many diagnostic codes have documented factory fixes or software updates.
Perform a thorough visual inspection of the wiring harness and connectors associated with Bank 1 Sensor 2. Look for damaged insulation, corrosion buildup, bent pins, missing weather seals, or any signs of heat damage from the exhaust.
Check electrical values at the sensor connector using a multimeter. Verify proper reference voltage from the ECU, confirm adequate ground resistance, and measure signal circuit continuity. Compare your findings against manufacturer specifications.
Conduct a wiggle test on the harness while monitoring the scanner's live data stream. Any signal dropouts or irregularities during movement indicate broken wires hidden inside the insulation.
Clear the code and perform a complete drive cycle that recreates the conditions shown in the freeze frame data. Recheck for P0137 after the test drive—if it returns, the underlying fault remains active.

Repair Options

Addressing P0137 typically involves one of three repair approaches, listed here from least to most expensive:

Wiring harness repair or connector replacement: $80–$250
Oxygen sensor or related actuator replacement: $150–$500
Control module diagnosis and repair: $300–$1,000

Total Repair Cost

The final cost depends entirely on which component triggered the code. At independent shop labor rates, expect to pay between $80 and $1,000 for a complete resolution. Starting with visual inspection and electrical testing before purchasing replacement parts prevents unnecessary expense—the worst-case scenario is rarely the first thing to check.

Can You Drive with P0137?

In most situations, the vehicle remains drivable, though you may notice reduced performance, slightly elevated fuel usage, or a disabled辅助系统 depending on your particular make and model. However, if the car exhibits stalling, failure to start, or warnings affecting braking and steering systems, treat this code as urgent and seek immediate repair.