Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. P0140 OBD-II Trouble Code: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)

P0140 OBD-II Trouble Code: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)

Check Engine Light

P0140 code definition

O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)

What the P0140 code means

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).

What causes the P0140 code?

  • 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

What are the symptoms of the P0140 code?

  • The Check Engine Light will come on, indicating a problem

  • Rough running

  • 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)

How does a mechanic diagnose the P0140 code?

  • 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)

Common mistakes when diagnosing the P0140 code?

  • Check the mass airflow sensor for proper operation and contamination before replacing the O2 sensor.

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.

How serious is the P0140 code?

  • 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.

What repairs can fix the P0140 code?

After scanning and clearing all fault codes and verifying the failure:

  • Test the O2 sensor to see if it changes when the fuel mixture is enriched
  • Test the mass airflow sensor for the proper readings per specifications
  • Replace the O2 sensor if contaminated or fails tests
  • Replace the mass airflow sensor if contaminated or fails tests
  • Clean out the mass airflow sensor to see if readings change

Additional comments for consideration regarding the P0140 code

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.

Need help with a P0140 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...

Related questions

Q: Q: Starting problem

At 180.000 miles, it could be just about anything. The P0161 and P0140 codes are oxygen sensor codes, and probably don't have anything to do with the starting issue, though you should have that investigated. The P0300 code however is...

Q: I'm wondering if it'll be a good idea to take out the whole ac compresser from my car?

The check engine light is supposed to come on if the controller detects a problem with the car that would effect the vehicle emissions. So it warns you of bad sensors, air leaks, misfires, overheating, and that sort of thing....

Q: eva PO597 engined coolant thermostat heater control circuit from obd diagnostic tool

Hi there. For the code P0597 to appear, there is an issue with the engine cooling system. Check the harness to the thermostat housing and a good connection and make sure that there is corrosion. Check for any coolant leaks...