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P0139 fault-error code 02 SENSOR CIRCUIT SLOW RESPONSE BANK1 SENSOR2

Updated: Aug 26

What is P0139 Fault-Error Code?

 

P0139 fault-error code is a fault code that can occur when the vehicle has an OBD-II (On-Board Diagnostics II) system. This code is identified as "HEATED 02 SENSOR CIRCUIT SLOW RESPONSE (BANK 1, SENSOR 2)". This definition means:

 

HEATED 02 SENSOR CIRCUIT: Refers to an oxygen sensor (O2 sensor) located in the vehicle's exhaust system. This sensor measures the oxygen level in the exhaust gases and helps adjust the vehicle's fuel-air mixture correctly.

 



SLOW RESPONSE: In the event of a malfunction of the O2 sensor, it indicates that there is a problem in the speed at which the sensor sends data to the ECU (Engine Control Unit) about the composition of the exhaust gases. This may mean that the sensor is slow or ineffective at adjusting the fuel-air mixture correctly.

 

BANK 1, SENSOR 2: The term "Bank 1" refers to a group of cylinders in the vehicle's engine. "Sensor 2" usually refers to the sensor that comes after the exhaust manifold outlet. This term indicates which sensor in the vehicle's exhaust system is experiencing problems.

 



What are the symptoms of P0139 Fault/Error Code?

 

Fault/error code P0139 usually occurs with the following symptoms:

 

Decrease in Engine Performance: It is possible for the vehicle to experience a loss of power or a significant decrease in its performance. This can occur when the O2 sensor provides incorrect data.

 

Decreased Fuel Economy: If the vehicle is consuming more fuel than normal or fuel economy is lower than expected, it may be a sign that the O2 sensor is slow or not providing accurate data.

 

Engine Fluctuation: Unstable engine operation or fluctuations in idle speed are also symptoms of code P0139. This may occur due to incorrect fuel-air mixture.

 



Increase in Exhaust Emissions: More emissions than normal coming out of the vehicle's exhaust can occur when the O2 sensor provides incorrect data.

 

Vehicle Shaking: Vehicle shaking or vibrations may be due to disruptions in the combustion process, which may indicate that the O2 sensor is not working properly.

 


P0139

What could be the causes of P0139 Fault/Error Code?

 

Fault/error code P0139 is usually caused by the following reasons:

 

Oxygen Sensor Malfunction: The P0139 fault/error code usually occurs when the O2 sensor (oxygen sensor) is malfunctioning or not working properly. This fault code can be generated if the sensor sends incorrect data or reacts slowly.

 



Wiring and Connection Problems: Problems with the cables or connection points between the oxygen sensor and the vehicle ECU. Problems such as corrosion, cable breakage, or loose connections can cause this type of failure.

 

Exhaust System Leaks: Leaks in the exhaust system can prevent the O2 sensor from collecting accurate data or cause inaccurate results.

 

Poor Engine Fuel-Air Mixture: The engine's fuel-air mixture is a factor that affects the correct operation of the O2 sensor. Things like an improperly adjusted injector, a clogged air filter, or an intake manifold leak can cause an uneven mixture.

 



ECU Problems: Rarely, a malfunction or software error in the vehicle's ECU can also cause the P0139 fault/error code to appear. However, this usually must be investigated to rule out other possible causes.

 

What Steps Should Be Followed to Resolve the P0139 Fault/Error Code?

 

The following steps can be followed to solve the P0139 fault/error code:

 

Reading the Error Code with an OBD-II Scanner: The first step is to read the P0139 code using an error code scanner that connects to the vehicle's OBD-II port. This helps determine the exact nature of the fault.

 

Checking the Oxygen Sensor: The oxygen sensor (O2 sensor) is used to control emissions in the vehicle's exhaust system. To ensure correct operation of this sensor, the physical condition and connections of the sensor should be checked. If the sensor is dirty, damaged or aged, it may need to be replaced.




 

Cable and Connection Check: Cables and connection points between the O2 sensor and ECU should be checked. If problems such as corrosion, cable breakage, or loose connections are found, these must be corrected.

 

Exhaust System Check: Leaks or blockages in the exhaust system can prevent the O2 sensor from working properly. The exhaust system should be inspected and necessary repairs made.

 

Adjusting Fuel-Air Mixture: It is important that the engine has the correct fuel-air mixture. The condition of the injectors, air filter and intake manifold should be checked and adjustments made if necessary.

 



ECU Software Update: In rare cases, a software error in the vehicle's ECU can cause code P0139. In this case, the ECU may need to be updated or reprogrammed.

 

Erase the Fault Code and Test Drive: After the problem is resolved, the fault code should be cleared with an OBD-II scanner. The vehicle should then be taken for a test drive and checked to see if any symptoms or fault codes return.

 

These steps are generally common steps to solve the P0139 fault code. However, each vehicle and situation may be different, so it is best to take your vehicle to an auto service or mechanical specialist to ensure proper diagnosis and resolution.

 



What are the Long-Term Effects of the P0139 Fault/Error Code?

 

The long-term effects of a P0139 fault code can often have a negative impact on the vehicle's performance, fuel economy and emissions. These effects may include:

 

Performance Reduction: If the O2 sensor is not working properly, it may affect the performance of the vehicle. Incorrect fuel-air mixture can cause rough engine operation or loss of power.

 

Increase in Fuel Consumption: If the oxygen sensor provides incorrect data, it may cause an increase in the fuel consumption of the vehicle. This may cause the vehicle to consume more fuel and therefore lower fuel economy.

 



Increased Emissions: Improper operation of the O2 sensor can increase the vehicle's exhaust emissions. This means greater release of environmentally harmful gases into the atmosphere and, accordingly, problems may arise in meeting emission control requirements.

 

Long-Term Damage: Operating the vehicle with the P0139 fault code for a long time may damage the engine and exhaust system. The wrong fuel-air mixture can overload components in the exhaust system or cause damage to the engine's combustion chamber.

 

Driving Safety Risk: Irregular operation of the vehicle or a decrease in its performance may adversely affect driving safety. This may cause difficulty in vehicle control or sudden loss of power, creating a potential risk of accidents.

 



It is important that the P0139 fault/error code is not ignored and resolved as soon as possible. It plays an important role in the long term in terms of the vehicle's performance, safety and environmental impact. Therefore, when you receive this fault code on your vehicle, it is important to consult an auto service or a mechanical expert and have the problem resolved.

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