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The performance of your vehicle’s engine relies heavily on maintaining the right air-to-fuel mix for combustion. The engine control module (ECM) determines the proper ratio by collecting data from different sensors within the air intake, fuel injection, and exhaust systems.

Oxygen sensors allow the ECM to determine the amount of oxygen in the car’s exhaust stream. A code P0136 gets set when on-board diagnostics detects a malfunction with the O2 sensor behind the light-off catalytic converter on bank 1. That’s the converter that deals with oxides of nitrogen and it needs to run very hot very quickly, which is why it’s so near the engine.

Some systems have a second catalytic converter behind the one closest to the engine on each bank, and that one deals with hydrocarbons and carbon monoxide. That converter isn’t monitored by an O2 sensor or anything else.

an oxygen sensor
Code P0136 means that the Bank 1 oxygen sensor is not operating correctly.

What Does the P0136 Code Mean?

Diagnostic trouble code (DTC) P0136 stands for “O2 Sensor Circuit (Bank 1, Sensor 2).” It refers to the same malfunction as the engine code P0137, except it applies to the second O2 sensor on Bank 1. The P0136 code triggers when the ECM believes that the Bank 1 O2 sensor is not operating correctly.

Because this is a generic code, it’s supported by various makes and models. Therefore, the steps for diagnosis and repair for a code P0136 in Ford vehicles may differ from, say, that of a Toyota.

As was mentioned, the O2 sensors collect oxygen levels in the exhaust. The ECM uses the data from the upstream (before the converter) O2 sensor to help calculate the amount of fuel the engine needs.

On the other hand, the ECM primarily uses the signal from the downstream (after the converter) O2 sensor to measure the efficiency of the catalytic converter. A traditional zirconia O2 sensor relays this information by producing a voltage between 0. V and 0.9 V.

A low voltage reading signifies that the exhaust is lean (too little fuel) and too little fuel burns in the combustion cylinders. A high voltage reading means the exhaust is rich (too much fuel) and tells the ECM to reduce the amount of fuel delivered to the engine.

If you’re thinking about fixing P0136 yourself, you’ll find more information that can help you solve the issue in our discussion about what oxygen sensors do and how OBD codes are stored depending on their operation.

mechanic holding an oxygen sensor
Malfunctioning oxygen sensor circuit issues can trigger P0136 code.

What are the Possible Causes of the P0136 Code?

There are several probable reasons why a scanner registers the P0136 code. They include:

  • Malfunctioning oxygen sensor
  • Malfunctioning oxygen sensor circuit issues (open, short, or high resistance)
  • Leak in the exhaust system
  • Corroded oxygen sensor connector
  • Faulty PCM (defective or requires software upgrade)

What are the Common Symptoms of the P0136 Code?

In most cases, this diagnostic trouble code does not come with any symptoms that affect the drivability of your vehicle. So it only has one prominent indication:

Check Engine Light is on or blinking

On-board diagnostics may switch on the Check Engine Light for a wide variety of trouble codes. You will need to connect your vehicle to a scan tool or code reader to determine whether the system has logged a P0136 code.

How to Diagnose the P0136 Code

To resolve the P0136 code, you need to determine its exact cause, which can prove challenging. If you are not confident with your DIY automotive repair skills, it’s best to leave the task to your trusted mechanic. Otherwise, you can track down the code and determine what’s causing it.

Need to refresh your knowledge of the P0136 code? Watch this helpful video:

How to Fix the P0136 Code

Because there is no one-size-fits-all solution for most OBD-II trouble codes, it can be difficult to resolve the P0136 code. You need to have the necessary tools, DIY skills, and automotive repair knowledge for the task. If you lack any of these, it may be best to let an expert deal with the problem.

If you have the right tools on hand and are confident with your DIY skills and automotive know-how, feel free to tackle the issue. Start by identifying the root cause of the P0136 code. When in doubt, consult online auto repair resources and guides.

Repair instructions may vary depending on your vehicle’s make and model, so don’t forget to check your owner’s manual before attempting to resolve the trouble code.

Want to be prepared for any future repairs your vehicle may need? Invest in an ALLDATA single-vehicle subscription. Not only will it help you keep your automotive knowledge and skills sharp, but it’ll also give you in-depth takes of various vehicle issues.

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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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