What is OBD-II Code P23B6 – NOx Sensor Supply Voltage Circuit Bank 1 Sensor 3

What is OBD-II Code P23B6 – NOx Sensor Supply Voltage Circuit Bank 1 Sensor 3

As a mechanic, I come across different OBD-II codes every day, and one common code that car owners bring their vehicles in for is Code P23B6. This code relates to NOx or nitrogen oxides sensors and a fault in the supply voltage circuit for the sensor in bank 1, sensor 3. The NOx sensor is a critical component of the exhaust system, so it’s essential to understand what this code means and how to fix it. In this article, I will explain everything about OBD-II Code P23B6, including its causes, symptoms, and solutions.

What is OBD-II Code P23B6?

The P23B6 is an OBD-II code that stands for NOx Sensor Supply Voltage Circuit Bank 1 Sensor 3. It means there is a problem with the NOx sensor’s power supply circuit in the engine bank 1, sensor 3. The code is usually set when the power supply voltage for the NOx sensor falls below the predetermined range of the manufacturer. The NOx sensor’s primary function is to detect nitrogen oxide levels in the catalytic converter and report them to the powertrain control module (PCM). If the PCM detects a fault in the NOx sensor supply voltage circuit, it sets this code.

What are the Causes of Code P23B6?

Code P23B6 can be triggered by various reasons, including:

1. Malfunctioning NOx sensor: The NOx sensor’s internal components, such as the heater or catalyst, may fail, leading to this code. This problem typically happens over time and can result from extended use of the vehicle.

2. Corroded or damaged pigtail connectors: If the connectors between the NOx sensor and the PCM become corroded, loose, or damaged, it can result in a faulty voltage supply circuit.

3. Short or open circuits in the NOx sensor wiring: The NOx sensor wiring can be damaged due to external factors such as road debris, corrosion, friction, or poor installation. This can cause an open circuit or short inside the wiring, which will trigger the code.

4. Failed PCM: A defective PCM is the least likely cause of code P23B6. However, if everything else has been ruled out, it may be necessary to replace the PCM.

What are the Symptoms of Code P23B6?

The symptoms of code P23B6 may vary, but the most common ones are:

1. Check Engine Light: The most visible symptom of this code is the illumination of the check engine light (CEL). The light indicates there’s an issue with the engine, and you should have it checked as soon as possible.

2. Poor Engine Performance: The engine may not run as smooth as it usually does and may experience power loss, misfires, or hesitation. It’s essential to address this issue immediately to avoid further damage to the engine.

3. High Fuel Consumption: When the NOx sensor isn’t working correctly, it can cause the engine to use more fuel. A noticeable decrease in fuel economy may result, and the engine may run hotter than usual.

How to Diagnose Code P23B6?

To diagnose code P23B6, you’ll need an OBD-II scanner to retrieve and read the code. First, clear the code and take a test drive to see if it reappears. If it does, these are some steps you can take to diagnose the issue:

1. Check the NOx sensor wiring for any damage or corrosion.

2. Use a multimeter to check the voltage and continuity in the NOx sensor wiring and pigtail connectors.

3. Inspect the NOx sensor’s functionality using a voltmeter or oscilloscope. The sensor should have a proper response to tests, and its resistance should not be outside the manufacturer’s specifications.

4. Inspect the power supply circuit from the PCM to the NOx sensor for any damage.

How to Fix Code P23B6?

Once you have diagnosed the issue, there are several steps you can take to fix code P23B6:

1. Repair or replace any damaged wiring or connectors in the NOx sensor or power supply circuit. Ensure all connections are clean, tight, and free of corrosion.

2. Replace the NOx sensor if it’s malfunctioning. Before replacing it, ensure that the power supply circuit and wiring are in good condition and that there are no other issues present.

3. If necessary, replace the PCM if everything else has been ruled out.

Frequently Asked Questions:

1. Is it safe to drive with code P23B6?
Answer: It’s not recommended to drive with code P23B6 because it can damage your engine, reduce fuel efficiency, and harm the environment. Get your vehicle checked right away by a qualified mechanic.

2. Can I clear code P23B6 on my own?
Answer: Yes, you can clear the code on your own by using an OBD-II scanner and clearing it from the diagnostic trouble code menu. However, clearing the code will only turn off the check engine light, but it won’t fix the underlying issue.

3. How much does it cost to fix code P23B6?
Answer: The repair cost for code P23B6 may vary, depending on what specific repair is required. Typically, fixing this code will involve an inspection of the NOx sensor and the power supply circuit, with repair or replacement, if necessary. The cost may range from a few hundred to a few thousand dollars.

4. Is code P23B6 common?
Answer: Code P23B6 is not one of the most common codes you’ll encounter, but it is still relatively common among diesel-powered engines.

5. Can I prevent code P23B6 from occurring?
Answer: Although some factors leading to this code are impossible to control, regular maintenance and service can help prevent it. Ensure that your vehicle has routine tune-ups, oil changes, and filter changes to keep it running smoothly and avoid long-term harm.


In summary, code P23B6 relates to a problem with the NOx sensor’s supply voltage circuit in the engine bank 1, sensor 3. A malfunctioning NOx sensor, corroded or damaged pigtail connectors, short or open circuits in the NOx sensor wiring, or a failed PCM are the most common causes of this code. The symptoms include a check engine light, poor engine performance, and high fuel consumption. To diagnose and fix code P23B6, you’ll need an OBD-II scanner to retrieve and read the code, check the wiring, test the NOx sensor’s functionality, and repair or replace any damaged components. Regular maintenance and service can help prevent code P23B6, so make sure your vehicle has routine tune-ups, oil changes, and filter changes.

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