P0137 Code – O2 Sensor Circuit Low Voltage

The P0137 diagnostic trouble code (DTC) indicates that the Engine Control Unit (ECU) has detected a low voltage signal from the oxygen sensor on Bank 1 Sensor 2. The downstream oxygen sensor (Sensor 2) is located after the catalytic converter and is used to monitor catalytic converter efficiency and emissions performance. When the ECU detects that the sensor voltage drops below the expected range, it stores the P0137 code and turns on the Check Engine Light. What Is Bank 1 Sensor 2 Oxygen sensors are installed in the exhaust system. Bank 1 – engine side containing cylinder 1 Sensor 1 – upstream oxygen sensor before the catalytic converter Sensor 2 – downstream oxygen sensor after the catalytic converter The downstream sensor mainly monitors catalytic converter performance rather than adjusting the fuel mixture. Common Causes of the P0137 Code Several problems may trigger the P0137 code. Faulty oxygen sensor A worn or damaged oxygen sensor may produce a weak voltage signal. Exhaust leaks Leaks near the oxygen sensor may allow extra oxygen into the exhaust stream. Damaged wiring Broken wires or corroded connectors may reduce sensor voltage. Catalytic converter issues A failing catalytic converter may affect downstream sensor readings. Fuel mixture problems An excessively lean mixture may cause low sensor voltage. Symptoms of the P0137 Code Drivers may notice several symptoms. Common signs include: Check Engine Light reduced fuel efficiency increased emissions failed emissions test In most cases, engine performance is not heavily affected. How to Diagnose P0137 Diagnosing this issue requires several steps. Step 1 – Scan the vehicle Confirm the P0137 code with an OBD2 scanner and check for related codes such as: P0136 P0138 P0140 P0420 Step 2 – Inspect the oxygen sensor Check the Bank 1 Sensor 2 sensor for contamination or damage. Step 3 – Inspect wiring and connectors Look for loose connectors, broken wires or corrosion. Step 4 – Monitor live data Using a scan tool, monitor downstream oxygen sensor voltage during engine operation. Repair Solutions for P0137 Typical repair solutions include: replacing the downstream oxygen sensor repairing damaged wiring fixing exhaust leaks addressing fuel mixture issues Most cases are solved by replacing the oxygen sensor. Estimated Repair Cost Typical repair costs include: Repair Estimated Cost Oxygen sensor replacement $120 – $350 Wiring repair $80 – $250 Exhaust leak repair $150 – $400 Can You Drive With Code P0137 Driving with P0137 is usually possible for short periods. However, ignoring the problem may lead to: higher emissions catalytic converter damage failed emissions inspection Repairing the issue promptly is recommended. FAQ – P0137 Code What does P0137 mean The P0137 code indicates low voltage from the downstream oxygen sensor circuit. Can a bad O2 sensor cause P0137 Yes. A faulty downstream oxygen sensor is the most common cause. Is P0137 serious It is usually moderately serious, mainly affecting emissions monitoring. How do you fix P0137 Start by checking the downstream oxygen sensor and its wiring connections.