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P0140 is a diagnostic trouble code (DTC) for "O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
P0140 is the OBD-II generic code which indicates that the O2 sensor for Bank 1, Sensor 2 failed respond to the fuel cutoff or fuel enrichment signals by the Engine Control Module (ECM).
The ECM determines that the O2 sensor has no activity
The O2 sensor for Bank 1, Sensor 2 does not respond (does not have a voltage change between 410-490 mV) to the fuel cutoff or fuel enrichment signals from the ECM for more than 74 seconds
The O2 sensor and mass airflow sensor comparison is misinterpreted by the ECM
The ECM could be malfunctioning in the O2 circuit
The Check Engine Light will come on, indicating a problem
Hesitation (upon acceleration after a deceleration phase)
The ECM loses the ability to keep the fuel system air-to-fuel ratio correct (could cause erratic driving symptoms)
Scans codes and documents freeze frame data
Monitors the O2 sensor data to see if the voltage is is moving above or below 410-490 mV
Monitors the mass airflow sensor data for responses to throttle changes, per specifications
Follows the manufacturer's specific pinpoint tests for further diagnosis of the code (tests differ between manufacturers)
The no response of the O2 sensor can be caused by a mass airflow sensor being contaminated and not calculating the amount of air entering the engine on the intake side.
This code can be due to problems with the mass airflow sensor, which is needed to calculate the proper amount of air entering the engine. Along with the O2 sensors, failure of any of these components will cause the ECM to miscalculate the air/fuel ratio going into the engine.
The ECM can lose control or get the wrong input from sensors like the mass airflow sensor or the O2 sensor if they are within specification but incorrect.
These problems can cause erratic drive complaints, which can compromise a driver's safety.
After scanning and clearing all fault codes and verifying the failure:
The no response of an O2 sensor may be due to a mass airflow sensor that is contaminated from things like oil from an oil impregnated air filter, as is common to all sensors. This oil coats the sensor and can cause it to become inaccurate. Cleaning the sensor may or may not fix the problem.
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