P0140: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)

What the P0140 error code means

P0140 is a check engine light diagnostic trouble code that translates to “O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)." Here, O2 refers to oxygen; sensor 2 on cylinder bank 1 is an oxygen sensor downstream of the engine's catalytic converter, which is part of the exhaust system. This code is triggered when the powertrain control module detects no activity from that particular sensor for a certain amount of time.

Why it's important to address this code

This specific oxygen sensor helps monitor the efficiency of the catalytic converter, which is a piece of emissions equipment that turns harmful pollutants and unburned fuel into less harmful byproducts, such as carbon dioxide and water. If the catalytic converter is not performing as expected, the result can be increased levels of pollutants in the exhaust, which may cause the vehicle to fail an emissions test and may damage the vehicle's emission controls.

Can I safely drive my car with this error code?

It is usually OK to drive a vehicle with the P0140 code present. Because this sensor is used to monitor emissions but generally not for adjusting fuel going into the engine, there shouldn't be any impact on drivability. However, leaving this problem unchecked can lead to issues when it's time to inspect or test the vehicle for registration, and it may be a sign that the vehicle is unnecessarily spewing harmful pollutants.

Common symptoms of code P0140

• The check engine light is illuminated.
• The vehicle fails an emissions test.
• The exhaust coming from the tailpipe contains high levels of harmful pollutants.

How the P0140 code is diagnosed

• Use an OBD-II scanner: Confirm the presence of the P0140 code and check for any related error codes before proceeding. It's possible that the P0140 error is being caused by another system problem.
• Inspect the sensor and associated wiring: Check the sensor itself and any wiring leading to or from it, as well as the connectors that bridge them; ensure that these parts are not corroded, melted or visibly damaged. It's also worth confirming that the vehicle's catalytic converter is still in place because these parts are a target for theft.
• Use a scan tool or oscilloscope: A mechanic will monitor the signal coming from the sensor to determine if it is functioning correctly.
• Test the powertrain control module: If no other issues are found, the powertrain control module itself may be faulty and require further testing, a reset or replacement.

How the P0140 code is repaired

• Replace a faulty oxygen sensor.
• Replace damaged wiring or connectors leading to the oxygen sensor.
• Replace a failing or missing catalytic converter.
• Reset or replace the powertrain control module.

Related reading

Follow the link below to reach our diagnostic check engine trouble codes catalog:
On-board diagnostics (OBD-II) trouble code directory