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P0136 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P0136 is defined as the Oxygen Sensor Circuit Malfunction (Bank 1, Sensor 2). It indicates a fault in one of the two oxygen sensors (sensor 2) located in the bank1 side of the engine.

Meaning

There are two oxygen (O2) sensors on the bank1 side of each car’s engine. Bank1 sensor1 is located near the engine itself while bank1 sensor2 is located on the engine’s exhaust pipe, usually next to the engine’s catalytic converter.

Both of these oxygen sensors are responsible for measuring the level of oxygen in the car’s exhaust. This information is transmitted to the car’s engine control module in the form of voltage readings, which uses this information to regulate the engine’s fuel injector pulse. In the case of a rich oxygen reading, the voltage reading on the oxygen sensor is high while in case of a lean oxygen-exhaust ratio, the voltage reading on the oxygen sensor is low. If the ECM experiences a low or lean oxygen-exhaust ratio for a prolonged period of time, then the P0136 DTC code sets in. 

Long story short, default code P0136 occurs when the bank1 oxygen sensor 2 detects a lean or low oxygen to exhaust ratio for a prolonged period of time (generally between 2 to 4 minutes). 

Causes

The P0136 error can be caused as a result of multiple reasons. Some of the most common causes are listed below:

  • A fault in the bank 1 oxygen sensor number 2. This could cause the sensor to misinterpret the exhaust-oxygen ratio, hence, resulting in P0136.
  • A leak in the exhaust pipe near the oxygen sensor 2 can lead to misinterpretation of the oxygen-exhaust ratio by disturbing the oxygen-exhaust mix.
  • An intake leak can also lead to the occurrence of P0136. Explaining it further, an intake leak refers to a situation where the vacuum seal of the exhaust system is compromised at any stage ranging from the fuel intake at the fuel chamber all the way up to the carburetor, where the air and fuel are mixed. 
  • The Bank1 sensor2 may have a damaged or corroded connector, which can result in a faulty voltage reading on the oxygen sensor. 
  • Oxygen sensors use an electric circuit to heat the exhaust in order to improve their efficiency in detecting the oxygen-exhaust ratio. A broken or damaged circuit wiring on the oxygen2 sensor may also cause the P0136 error to set in.

Symptoms

It is not necessary for visible symptoms to appear each time when P0136 sets in. However, the commonly experienced symptoms include:

  • An illuminated ‘check engine light’
  • Engine may start to misfire
  • A reduced fuel consumption efficiency often referred to as low mileage
  • Increase in the amount of exhaust emissions from the tailpipe

Diagnosis

Steps for Self-diagnosis:

When you notice the illuminated check engine light, that is a signal for you to visually inspect the engine and its nearby wiring and connections. If you suspect P0136 fault code, you should check the bank1 sensor 1 area for any frayed or damaged wiring and connectors. 

You can also inspect the catalyst for any leakages that may be causing P0136 to arise.

You may also want to inspect the bank1 sensor2 circuit for any damaged or burnt wiring. 

Steps for professional diagnosis:

The technician will follow the below mentioned protocols to diagnose and fix DTC P0136:

  • First and foremost, the technician will scan the Engine Control module (ECM) for fault codes and will freeze frame this information. He/she will then move forward to clearing the codes from the ECM to verify if the fault codes reappear, confirming the presence of the fault.
  • Next, the technician will monitor the bank1 oxygen sensor2 to see if the voltage is fluctuating between high and low more frequently than in other sensors - as the presence of this issue is an indication of a faulty Oxygen sensor which needs to be replaced.
  • The technician will check the wiring linked to the oxygen sensor2 for any damage or burns.
  • The technician will also check the Oxygen sensor’s heat circuit and its resistance
  • The technician will look for any vacuum leaks in the exhaust shoot, especially near the bank1 oxygen sensor2.

Common mistakes in diagnosis:

Here are the common errors which you should try to keep an eye out for when you take your car for having it examined by a professional car technician: 

  • The technician may skip the step of checking and repairing any leaks in the exhaust near the sensor and could directly resort to changing the oxygen sensor. Simply by repairing these leakages, the oxygen sensor can begin to show correct readings. 
  • The technician may not check the O2 sensor for corrosion and buildup from engine oil leakages. Simply cleaning the oxygen sensor can also help resolve the issue.
  • The technician may hastily replace the damaged oxygen sensor without getting to the root cause of the damage. The damage to the oxygen sensor could be due to a faulty catalyst which would also require a replacement. 
  • In case of a damaged harness, proper repairs should be made including any required replacements in order to avoid further damage. 
  • Follow the manufacturer specified steps to pinpoint and eliminate fault code P0136.

How serious is this?

If the P016 default code is experienced for a prolonged period, it means the engine has to operate under rich conditions for a long time. Such an extended exposure is likely to damage many critical engine parts.

many critical engine parts. 

How to fix this?

Replacing the Bank1 Oxygen Sensor 2 remains the last resort that is one quick way of getting rid of the P016 default code. Other ways to fix the P01336 default code include replacing any frayed wires or connectors as well as repairing any leakages that allow for air to escape from the engine. The catalyst can also be repaired to eliminate P0136 fault code in some cases.

Related codes

Fault code P0136 is closely related to fault code P141. Other related codes include P0137 and P0130.

Conclusion

Regular visits to the technician for engine servicing and cleaning can help in timely detecting, if not avoiding, fault code P0136. In this way, any compromised or replaceable components can be detected in time to avoid greater damage.