If you own a car or are planning to buy one, it is important that you are aware of the various codes that your car may throw.
One such code is P0138, which is related to the O2 sensor circuit. In this article, we will discuss what P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2) means, its symptoms, causes, diagnosis, and prevention.
What is P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)?
P0138 is a diagnostic trouble code (DTC) that is related to the O2 sensor circuit. The O2 sensor monitors the oxygen level in the exhaust system and sends this information to the engine control module (ECM).
The ECM then adjusts the air-fuel mixture accordingly.
P0138 specifically refers to a low voltage output from the O2 sensor located downstream of the catalytic converter on the bank 1 side of the engine.
Symptoms of P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
The symptoms of P0138 may vary from one car to another, but some of the common symptoms include:
- Check engine light is on
- Poor fuel economy
- Rough idling
- Stalling or hesitation during acceleration
- Failed emissions test
- Reduced engine power
Causes of P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
The most common causes of P0138 are:
- Faulty O2 sensor
- Wiring issues such as a short circuit or open circuit
- Loose or corroded connector
- Faulty ECM
- Exhaust leak before the sensor
- Failed catalytic converter
How to Diagnose P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
To diagnose P0138, you will need an OBD-II scanner. Follow the steps below to diagnose the issue:
- Connect the scanner to the OBD-II port and retrieve the code.
- Check the freeze frame data to determine the conditions when the code was set.
- Inspect the wiring and connector for any visible damage.
- Measure the voltage output of the O2 sensor using a multimeter.
- Check for any exhaust leaks before the sensor.
- Inspect the catalytic converter for any damage.
How to Fix P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
Once you have diagnosed the issue, you can then proceed with fixing it. Here are some methods you can use to fix P0138:
- Replace the O2 sensor
- Repair or replace any damaged wiring or connector
- Replace the catalytic converter if it has failed
- Replace the ECM if it is faulty
Prevention of P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
To prevent P0138 from occurring, you should:
- Replace the O2 sensor as recommended by the manufacturer
- Keep the engine tuned up
- Regularly inspect the wiring and connector for any damage
- Use high-quality fuel
- Avoid driving with a misfiring engine
P0138 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2) is a common issue that car owners may face. The symptoms may vary, but the most common include poor fuel economy, rough idling, and stalling.
The causes may range from a faulty O2 sensor to a failed catalytic converter. Diagnosing the issue requires an OBD-II scanner, and fixing it may involve replacing the O2 sensor, repairing or replacing any damaged wiring or connector, or replacing the catalytic converter or ECM.
To prevent P0138 from occurring, you should replace the O2 sensor as recommended by the manufacturer, keep the engine tuned up, regularly inspect the wiring and connector for any damage, use high-quality fuel, and avoid driving with a misfiring engine.
Is it safe to continue driving with a P0138 code?
- It is not recommended to continue driving with a P0138 code as it can cause serious damage to your engine and may lead to increased emissions.
Can I clear the code and ignore it?
- Clearing the code will only temporarily remove the check engine light, but it won’t fix the underlying issue. It is best to diagnose and fix the issue to prevent further damage.
Can a faulty O2 sensor cause other issues?
- Yes, a faulty O2 sensor can cause poor fuel economy, rough idling, and other issues related to the air-fuel mixture.
How often should I replace my O2 sensor?
- O2 sensors should be replaced as recommended by the manufacturer, typically around every 100,000 miles.
Can a failed catalytic converter cause a P0138 code?
- Yes, a failed catalytic converter can cause a P0138 code as it may affect the voltage output of the downstream O2 sensor.