Your vehicle’s powertrain control module (PCM) relies on oxygen sensors to adjust engine performance and control emission levels. When the oxygen (O2) sensor that monitors the exhaust from the catalytic converter stops working, the PCM may log the diagnostic code P0140.
What Does the P0140 Code Mean?
Diagnostic trouble code (DTC) stands for “Oxygen Sensor Circuit No Activity Detected (Bank 1, Sensor 2).” It indicates that the PCM perceives a problem with the post-catalytic monitoring oxygen sensor (the bank 1, sensor 2) circuit.
Found behind the catalytic converter, this sensor measures the oxygen levels in the exhaust after the converter breaks down the unburned fuel.
Note: Code P0316 is a generic code specified by the Society of Automotive Engineers (SAE). Depending on the car manufacturer, the code’s definition may change.
What Do Oxygen Sensors Do?
Oxygen sensors keep track of the oxygen levels in the vehicle’s exhaust system. They update the PCM on how efficiently the engine and the emissions control systems work.
To signal the PCM, the post-catalytic monitoring oxygen sensor generates voltage within a set range. If it detects high oxygen content that indicates a lean mixture, it will send a low-voltage signal. For low oxygen content and rich mixtures, it emits a high-voltage signal.
If the catalytic converter is in good condition, this oxygen sensor takes more time to change its voltage than the #1 sensor placed before the catalytic converter. Code P0140 may be set when the downstream O2 sensor’s signal remains within a certain range for longer than specified.
What are the Possible Causes of the P0140 Code?
You can narrow down the cause of the code P0140 to several possibilities. They include:
- Failed oxygen sensor
- Rear oxygen sensor wiring or connection issues
- Faulty PCM or software in need of an update
What are the Common Symptoms of the P0140 Code?
Common warning signs of a P0140 code include:
- Illuminated or blinking check engine light
- Increased tailpipe emissions
- Failed vehicle emissions test
Fortunately, most instances of a P0140 code don’t hamper the drivability of the car. The post-catalytic oxygen sensor only keeps an eye on the catalytic converter’s efficiency. In most vehicles, the PCM doesn’t use the data from this sensor as a primary input for adjusting the fuel sent to the engine.
However, you should still bring your car to a trusted auto repair shop if your scanner shows code P0140. Your vehicle’s emission levels may exceed the limits set by state and federal laws, which can cause your car to fail an emissions test.
How to Diagnose the P0140 Code
Learning how to diagnose and repair engine code P0140 can prove a handful. The videos below can help guide you through the diagnosis:
How to Fix the P0140 Code
Even though the symptoms, causes, and affected systems of OBD-II codes tend to overlap, there is no one-size-fits-all repair for them. The process for diagnosis and repair may vary based on the vehicle’s make and model. Let your mechanic take care of the P0140 code for a guaranteed fix.
If you are confident with your automotive knowledge and skills, the first step is to accurately pinpoint what triggered the P0140 code. Then, using online auto repair resources and guides, identify the most effective way to resolve the issue.
Supplement your task with an ALLDATA single-vehicle subscription to benefit from comprehensive and up-to-date factory repair information. Also, check your owner’s manual before implementing the solution to ensure it’s the right one for your vehicle.