P0137 — O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) #

Note: The description for code P0137 may vary depending on the vehicle manufacturer (OEM). Always consult your OEM service manual or trusted scan tool for the exact wording used by your brand.

• O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) – Generic (most OEMs)
• Oxygen Sensor Circuit Low Voltage (Bank 1, Sensor 2) – Ford, GM, Toyota
• Heated Oxygen Sensor 2 Circuit Low Voltage (Bank 1) – Honda, Nissan
• Lambda Sensor Low Voltage (Bank 1, Sensor 2) – BMW, Mercedes

Summary of Code P0137 #

P0137 is a diagnostic trouble code (DTC) indicating that the oxygen sensor (O2 sensor) located after the catalytic converter (Bank 1, Sensor 2) is reporting a voltage lower than expected by the engine control module (ECM) or powertrain control module (PCM). This sensor monitors the efficiency of the catalytic converter by measuring the oxygen content in the exhaust gases. When its voltage consistently drops below a certain threshold, it signals that something may be wrong with the sensor itself, the wiring, or the exhaust system. This code does not always mean the sensor is faulty—it could also point to issues like an exhaust leak or engine running conditions. Left unchecked, P0137 can affect fuel economy and emissions.

Common Symptoms for Code P0137 #

Drivers might not always notice immediate drivability issues with P0137, but some symptoms can develop over time. If the oxygen sensor fails to provide accurate readings, the ECM may not adjust the air-fuel mixture correctly, leading to potential side effects. Here are the most frequent signs:

• Check Engine Light (CEL) illuminated
• Decreased fuel efficiency (worse miles per gallon)
• Rough idling or hesitation during acceleration (less common)
• Failed emissions test or higher tailpipe emissions
• Sulfur or “rotten egg” smell from the exhaust (rarely)

Most Likely Causes of P0137 #

Several issues can trigger the P0137 code, but some are far more common than others. In most cases, the problem is electrical or related to sensor degradation, but mechanical faults or external influences can also play a role. Here’s the typical order of likelihood:

1. Faulty O2 sensor (Bank 1, Sensor 2): Sensor is old, contaminated, or worn out.
2. Wiring problems: Damaged, corroded, or broken wires/connectors in the O2 sensor circuit.
3. Exhaust leaks: Leaks upstream of the sensor can introduce excess oxygen, skewing readings.
4. Engine running rich: Excess fuel in exhaust can lower sensor voltage.
5. PCM/ECM software or internal faults: Rare, but possible if other issues are ruled out.

Step-by-Step Diagnostic for Code P0137 #

A methodical approach is key to accurately resolving P0137. Skipping steps can lead to unnecessary sensor replacements or overlooked issues. Here’s a standard workflow followed by master technicians:

• 1. Confirm the code: Use a scan tool to verify P0137 is active and note any related codes.
• 2. Inspect O2 sensor wiring and connectors: Look for frayed wires, corrosion, or loose connections.
• 3. Monitor live data: Check the voltage reading of Bank 1, Sensor 2. Normal range is typically 0.4–0.7V; P0137 signals a drop below about 0.1V for a sustained period.
• 4. Check for exhaust leaks: Inspect exhaust pipes, gaskets, and welds before and around the sensor for leaks.
• 5. Assess fuel trims and engine operation: Look for signs of the engine running rich (black smoke, high fuel trims).
• 6. Test the sensor: If possible, bench test the O2 sensor with a digital multimeter or swap with a known good sensor.
• 7. Rule out PCM/ECM faults: If all else checks out and the code persists, further diagnosis of the control module may be needed.

Possible Repairs for P0137 #

Once you’ve pinpointed the root cause of P0137, apply the appropriate fix. Not every case requires a new sensor—addressing wiring or external issues can often resolve the code. Here’s what may be involved:

• Replace the O2 sensor (Bank 1, Sensor 2) if it’s faulty or out of spec.
• Repair or replace damaged wiring/connectors in the sensor circuit.
• Seal any exhaust leaks upstream of the sensor (gaskets, welds, flanges).
• Correct rich running conditions (check fuel injectors, fuel pressure, air intake).
• Update or reprogram the PCM/ECM if a software issue is discovered (rare).

Is It Safe to Drive With Code P0137? #

Generally, you can drive cautiously with code P0137, but it’s not advisable for extended periods. While this code rarely causes immediate breakdowns, ignoring it can lead to reduced fuel efficiency, higher emissions, and potential long-term damage to the catalytic converter. If you notice worsening symptoms—like rough running or poor fuel economy—have the issue checked promptly.

Vehicles Most Commonly Affected by P0137 #

P0137 is a generic OBD-II code and can appear on virtually any modern gasoline-powered vehicle. However, some models are more frequently reported—often due to sensor placement, age, or known wiring vulnerabilities. Here’s a sample list:

• Chevrolet Silverado / GMC Sierra (2000s-2010s)
• Toyota Camry and Corolla (2000s-2010s)
• Ford F-150 (2000s-2020s)
• Honda Accord and Civic (2000s-2010s)
• Nissan Altima and Sentra (2000s-2010s)
• Chrysler/Dodge minivans and sedans (2000s-2010s)

Common Mistakes & Best Practices with P0137 #

Addressing P0137 can be straightforward, but some common pitfalls can lead to wasted time and money. Here’s what to avoid—and what to do instead:

• Replacing the O2 sensor without checking wiring or exhaust leaks first.
• Overlooking live data analysis (sensor voltage trends during operation).
• Ignoring related codes (e.g., fuel trim, misfire, or catalytic converter codes).
• Using low-quality aftermarket sensors—always opt for OEM or reputable brands.
• Not clearing the code after repairs (drive cycle may be needed to verify fix).

Quick FAQ for Code P0137 #

Have more questions about P0137? Here are answers to what vehicle owners and technicians often ask:

• Q: Does P0137 always mean my O2 sensor is bad?
  A: Not always—wiring issues, exhaust leaks, or engine problems can also cause this code. Always diagnose before replacing the sensor.
• Q: Will P0137 cause my car to fail an emissions test?
  A: It can—especially if the check engine light is on, as most states and regions automatically fail vehicles with active emissions codes.
• Q: Is it expensive to fix P0137?
  A: Costs vary: a sensor replacement is usually $100–$300 parts and labor, but wiring or exhaust repairs can be less or more depending on severity.