P0140 CODE: Causes and Fixes, O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)

The diagnostic code p0140 is a generic code triggered when the Bank 1, Sensor 2 02 Sensor fails to provide a response to either the fuel enrichment signals or fuel cut off as sent from the ECM (Engine Control Module).

If you are encountering this issue with your vehicle, there is no need to worry! This is among the most common error codes out there. While you can make your own troubleshooting attempts, I would recommend the help of an auto technician like me so that you will be able to find the exact problem that causes the error, and fix it accordingly without causing other problems.

Even though a failure in one of the sensors may sound like it is a major problem, reality dictates that it is but a natural part of the life cycle of any vehicle. This means that the sensors will fail inevitably. As such, they have to be replaced as the automobile is being used through the passing of time.

What Causes the Diagnostic Code p0140 Error?

There are a number of possible causes of the p0140 error code:

  • When the ECM (Engine Control Module) determines that there is no activity in the O2 sensor.
  • If there is no response from the O2 sensor for Bank1, Sensor, no response indicates that there is no change of voltage between 410 to 490 mV for over 74 seconds (from the fuel enrichment signals or fuel cut off as signaled by the ECM).
  • The possibility of the ECM not working well inside the 02 circuits.
  • The possibility of the ECM misinterpreting the comparison of the 02 sensors and the mass airflow sensor.

  • What Are the Symptoms of OBD2 Code p0140?

    The following are the 5 most common symptoms of p0140:

  • ‘Engine Malfunction’ and ‘Check Engine’ light is on
  • Burnt, shorted, or open oxygen sensor wiring
  • Corroded, loose, bent or disconnected pins of the oxygen sensor connectors
  • Faulty downstream oxygen sensor
  • Faulty or dirty Mass Air Flow (MAF) Sensor (which also causes p0101 error code)

  • How to Diagnose Error Code p0140

    Before you attempt to diagnose this error code, make sure that you have some knowledge regarding safety measures as you work with your car. If not, better take it to a professional like me. Avoid compromising safety – it's a must!

    1. First Setp

    In order to eliminate any potential intermittent DTC condition, it is helpful to clear the memory of the ECU first and then to complete a driving cycle. This includes reading trouble codes while noting them. This can also include clearing the memory that lists the data trouble codes and performing about a 5 to 10-minute driving cycle.

    If you notice the system’s Check Engine Light staying off, an intermittent problem is possible. If the light is on during the driving cycle, you may go on with the diagnostic process. 

    2. Visual Check

    Leaks from the exhaust, most particularly right before the oxygen sensor, may trigger output from the 02 Sensor. This can be identified as a condition of “no activity” by the Electronic Control Unit. This is the reason why it is vital to determine the condition of the exhaust pipe, repairing any link, including a faulty exhaust manifold gasket.

    To check whether there is a problem with the oxygen sensor connector and wiring, it is best to conduct a thorough visual check of the connectors and wirings of the downstream 02 sensors. Check out for signs of damaged, burnt, deteriorated or corroded wires. You can also unplug first the sensor, looking for any loose connections, bent terminal pins, corrosion, as well as a potential indication of a faulty connection. 

    3. Use A Scan Tool Test

    To conduct a downstream oxygen sensor test, you can turn the engine on, and enter the KOER mode. If the tool that you use for scanning features a graphing ability, you can turn it on. You can then simultaneously graph the engine 02 and RPM output.

    Then, you can increase to 2000 RPM. The voltage is roughly stable. After this, you can decrease the speed to idle, with the O2 output not having much variation. This procedure can be done several times.

    If the output of the downstream O2 sensor is closely similar to the output of the upstream oxygen sensor, then this could mean a faulty catalytic converter. When using these sensor tests, make sure to follow the instructions in completing the tests. 

    Read Next: Bypass Oxygen/O2 Sensor

    How to Repair Code p0140

    The solution to this error code may depend on the results of your diagnostics. This could include:

    1. Repair exhaust pipe
    2. Repair the connectors and wirings of the oxygen sensors
    3. Replacement of the downstream oxygen sensor
    4. Performing other needed diagnostics that are found on the catalytic converter.

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