Error Code P0137: Oxygen Sensor Circuit Low Voltage B1S2

If you start your car and your dashboard lights up like the Fourth of July, you're right to be alarmed. Multiple lights illuminating at once can yield a variety of OBD-II scanner error codes, including P0137.

What Does the Code P0137 Mean?

In short, there’s an issue with your vehicle’s oxygen sensors. Specifically, the diagnostic trouble code P0137 yields the following message: “O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2).” Here’s what that means:

Your vehicle has multiple oxygen sensors. Sensor 2, the subject of a P0137 error code, is downstream from the catalytic converter, and its job is to make sure the catalytic converter is working properly. To do that, it measures the ratio of air to fuel coming out of it. When it’s functioning correctly, the catalytic converter keeps the stoichiometric air to fuel ratio at 14.7:1.

Meanwhile, your vehicle’s power-train control module, or PCM, alternates between air-fuel mixtures. The composition of these mixtures depends on the info that the PCM gets from O2 sensor 1, which sits upstream.

When everything is operating properly, O2 sensor 2 outputs a 0.45-volt current. When something goes wrong in this cycle, and sensor 2’s output dips below 400 millivolts for 20 seconds or more, it triggers the low voltage error code.

What Can Cause Low Voltage in Sensor 2?

There are a handful of issues that can cause voltage to drop in O2 sensor 2. Some of the most common issues are the following:

  • An exhaust leak
  • A short in the O2 voltage circuit
  • Loose connections
  • Excessively high or low fuel pressure
  • An engine that’s running either very lean or very rich
  • A faulty O2 sensor

What Are the Symptoms of a P0137 Error Code?

Often, an OBD-II scanner error code P0137 problem has no symptoms. Other times, you might experience one of the following indications that you have an oxygen sensor issue:

  • The check engine light comes on.
  • Multiple other dash lights come on at the same time, such as traction control and four-wheel drive.
  • There’s a noticeable odor of exhaust fumes.
  • There are exhaust leaks near the affected O2 sensor.
  • Your car or truck runs and/or idles roughly.

Is It Safe To Drive With This Error Code?

For a short period of time, yes. Operating your vehicle for an extended period of time, however, can end up doing significant damage to your engine. The uncontrolled air to fuel ratio may also cause your vehicle to get extremely poor gas mileage.

How Do I Fix Trouble Code P0137?

There are several ways to troubleshoot a car or truck with this code:

  • Inspect the O2 sensor, its wiring, and its connections for visible damage, including corrosion and contaminated fluids.
  • Put the vehicle into accessory mode and monitor all the oxygen sensors’ data in real-time. Look for the affected sensor to toggle between high and low voltage faster than the other sensors.
  • Search for an exhaust leak before the affected sensor.

In the event that addressing these issues doesn’t solve the problem and clear the error code, it’s likely time to take your vehicle to a trusted mechanic for further testing as suggested by the manufacturer. Often, this error code ultimately results in one of two outcomes:

  • Repairing or replacing the affected sensor’s wiring/connection
  • Replacing the O2 sensor itself

Nobody knows your car or truck better than you do. When you suspect there’s a problem, using an OBD-II scanner is often the best way to begin pinpointing what’s wrong so you can fix it promptly and get back on the road, worry-free. While a P0137 error code isn’t severe, it does require immediate attention in order to avoid costlier repairs in the future.

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