P0140 Fault Code

Long Description

Fault code P0140 is logged when the powertrain control module (PCM) has detected an issue with the bank 1 heated oxygen sensor 2.

This occurs when there the ECU is not receiving any change in signal from the sensor, indicating that the sensor is not active.

A heated oxygen sensor is used to monitor the oxygen levels in a heated environment, typically the exhaust system. It contains a heater circuit within the sensor which brings the sensor up to the desired operating temperature to improve effectiveness.

Heated oxygen sensor 2 is found after the catalytic converter and monitors the oxygen content in the exhaust fumes once they have gone through the converter.

This information is relayed back to the ECU to help control the air-fuel mixture within the engine. This can help optimize performance and reduce emissions.

Bank 1 refers to the side of the engine in which cylinder 1 is located. This only applies to V-shape engines. Sensor 2 refers to this being the downstream oxygen.

Chevrolet, Hyundai, and Suzuki are some of the most notorious manufacturers to suffer from this fault code.

Other Signs of This Problem

A malfunctioning or defective downstream oxygen sensor has relatively few additional signs to help indicate the issue.

The most obvious sign will be the Check Engine light being illuminated – paired with this P0140 fault code appearing on an OBD2 reader. It is also possible for it to be blinking.

In some cases, there may be increased emissions from the exhaust tailpipes. This can include black smoke or odor.

If possible, an emissions test can also determine this type of issue. A defective downstream oxygen sensor can cause the ECU to allow excessive emissions into the exhaust fumes. This means the vehicle will fail an emissions test.

There may be other oxygen sensor faults logged as well. For other downstream sensor issues, see codes P0136 to P0141. Upstream sensor fault codes range from P0130 to P0135.

What Could Be The Problem?

Issues with heated oxygen sensors are typically limited to the sensor circuit itself. This is even more true for code P0140 which indicates only that the sensor is not active.

It is very likely that the sensor itself has failed. This can be a result of a damaged or faulty sensor.

Additionally, the sensor circuit can be the cause of the issue. Damaged or frayed wires can cause the signal from a working heated oxygen sensor to be lost. A loose connection also has this outcome.

In rare cases, a faulty PCM can cause this fault code. However, it is very likely that a faulty PCM will come with a host of additional fault codes being logged.

Fixes

The possible solutions to this fault code are mostly restricted to the heated oxygen sensor circuit after the catalytic converter.

A faulty or damaged heated oxygen sensor should be replaced.

Any issues with the circuit like damaged wires or loose connections need to be repaired.

If the PCM is running on outdated software, it must be updated. If it is faulty, it will need to be replaced.

Seriousness

Fault code P0140 should be considered moderate in terms of seriousness. There can be no driveability changes or risks to the vehicle and its components.

It is a good idea to have the issue resolved as soon as possible.