Code P0137 (Symptoms, Causes and How)

Today’s vehicles rely on a complex network of sensors, cables and modules to support efficient operation. The data shared over this network is processed by the vehicle’s ECM/PCM and used to calculate numbers such as injection timing as well as injector pulse width.

As a benefit of this data transmission, today’s highly efficient vehicles run much cleaner than ever. This is primarily due to the ability of most engines to determine the correct air/fuel ratio under any given load, with a high degree of accuracy.

A series of oxygen sensors are used to detect excessively rich/lean exhaust conditions, allowing these conditions to be corrected on the fly. However, oxygen sensors are prone to failure over time, presenting many problems in the future.

These problems are often highlighted by a sudden check engine illumination in a vehicle’s instrument cluster, indicating that an active diagnostic trouble code has been stored. Of these O2 sensor-related error codes, none may be as widespread as DTC P0137.

Read on to learn more about DTC P0137 and how to fix these problems if they occur.

What does the P0137 code mean?

The P0137 diagnostic trouble code indicates that the voltage is lower than expected at the output of oxygen sensor #2, located along bank 1. The P0131 code applies to oxygen sensor #1 .

Typically, this voltage must drop below 450 millivolts for a period of 20 seconds or more. This means that the #2 engine O2 sensor cannot provide reliable information to the engine ECM.

Because the #2 oxygen sensor is located downstream of a vehicle’s catalytic converter, the engine in question cannot determine downstream exhaust values. Therefore, the engine management software is prevented from obtaining an accurate picture of the combustion efficiency in the affected bank.

Related: Code P0134, Code P0135, Code P0136, Code P0138, Code P0140 Code P0157

Code P0137 Symptoms

Several symptoms can be associated with the P0137 diagnostic trouble code, although these symptoms often vary on a case-by-case basis. These are some of the most common symptoms associated with DTC P0137.

Causes of Code P0137

A P0137 diagnostic trouble code can be caused by a number of different conditions. The true root cause of such a problem can only be confirmed with a complete diagnosis.

However, here are some common causes of the P0137 code that every driver should know about.

Is the P0137 code serious?

Generally, DTC P0137 is considered quite serious. Although a vehicle with this code can almost always be driven, it is not recommended to do so unless absolutely necessary.

Since engine O2 sensors determine downstream combustion efficiency, inoperative components of this nature can allow many to slip through the cracks.

If an engine were to run lean for a long period of time, undetected by a faulty oxygen sensor, serious damage could occur. In fact, such a condition can lead to increased wear of internal components, burned pistons, and valve damage. After that, a complete disassembly may be required.

In any case, a vehicle with an active DTC P0137 should be taken to a reputable auto service center as soon as possible.

How to fix code P0137

The following steps will help you diagnose and fix the root cause of your vehicle’s P0137 trouble code. Additionally, it is always advisable to consult the specific factory service documents for your particular vehicle.

#1 – Check Additional Trouble Codes

Before starting the diagnostic process, it is important to verify that there are no other active fault codes stored. If additional codes are present, each must be carefully diagnosed to rule out any possible correlation.

#2 – Locate the sensor and physically inspect it

Below you will find oxygen sensor #2 (bank 1). After locating this sensor, check for damaged, pinched, or broken wires. Also, check that the sensor connector is securely locked.

Any defects noted must be corrected before continuing.

#3 – Check for exhaust leaks

It is also important to note that the main cause of your vehicle’s problems is a major leak. This can be achieved with the use of a smoke machine.

When connected to the vehicle’s exhaust duct, smoke escapes through all exhaust points. Any such leak must be repaired before continuing.

#4 – Check Fuel Pressure

Using a fuel pressure gauge, check that your vehicle has the correct fuel pressure when idling. Recorded pressure readings should mimic those found in specialized factory service documentation.

#5 – Find a vacuum leak

Unmetered air, such as air allowed into a leaky engine vacuum, can eventually cause a lean condition. Therefore, it is essential to find and repair any vacuum leaks found at this time.

In any case, a smoke machine can be used to locate these leaks with great precision.

#6 – Perform a voltage check

You will now warm up your vehicle to operating temperature and prepare to perform an O2 sensor voltage check. Unlike an upstream oxygen sensor, #2 oxygen sensors do not fluctuate continuously. Instead, a usable #2 O2 sensor should show only subtle voltage fluctuations.

In general, readings of this type should be between 0.1 V and 0.95 V, although readings typically average in the 0.5 V range. Any classification out of the spectrum during these tests requires the replacement of the sensor.