Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with a part of the car that helps it check pollution. The car has a sensor that gets warm to work properly, and it's not working right.
The P23B5 code indicates an issue with the heater circuit of the NOx sensor on Bank 1, Sensor 3. The sensor's heater is not performing within the expected range.
The NOx sensor measures the levels of nitrogen oxides in the exhaust gases. It has a built-in heater to ensure accurate readings by bringing the sensor to operating temperature quickly. The P23B5 code is triggered when the sensor's heater circuit is not performing as expected, either due to a circuit range or performance issue.
• Check Engine Light illuminated
• Poor fuel economy
• Failed emissions test
• Faulty NOx sensor
• Damaged wiring or connectors
• Blown fuse in the sensor circuit
NOx: Nitrogen oxides, pollutants produced during combustion.
OBD-II: On-Board Diagnostics, a system for self-diagnosing and reporting vehicle issues.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage.
• Test the NOx sensor heater circuit for proper voltage.
• Replace the faulty NOx sensor.
• Repair or replace damaged wiring or connectors.
• Replace any blown fuses in the sensor circuit.
• OBD-II scanner
• Multimeter
• Socket set
$200 - $600
Moderate
• Volkswagen Jetta
• Audi A4
• BMW 3 Series
• Regularly inspect sensor wiring for damage.
• Ensure proper maintenance of exhaust system.
• Use quality fuel to reduce sensor contamination.
Sensor Issue
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional.
• Avoid driving extensively with this code active.
Check your vehicle's warranty for emissions-related components, as they may be covered.
This code has become more common with the introduction of stricter emissions standards and the use of advanced NOx sensors.
Moderate – While the car may still be drivable, it is important to address the issue to avoid further emissions problems.
Driving with a malfunctioning NOx sensor may result in higher emissions, which can be illegal in areas with strict emissions regulations.
• Engine at operating temperature
• Vehicle in closed-loop operation
The NOx sensor is typically located in the exhaust system, downstream of the catalytic converter.
Q: What does a NOx sensor do?
A: A NOx sensor measures the levels of nitrogen oxides in the exhaust gases to help control emissions.
Q: Can I drive with a P23B5 code?
A: While the car may still operate, it's best to address the issue to avoid increased emissions and potential engine performance problems.
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Helpful when the code points toward exhaust or oxygen-sensor work and space is tight.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.