Oxygen sensors functional check: Introduction
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2017 BMW X3, 2016 BMW X3, 2015 BMW X3, 2014 BMW X3, and 2013 BMW X3. However, it is still accessible from the selected car via links, so may be relevant.
In vehicles with a diesel engine, up to two oxygen sensors (depending on the version) are installed to comply with exhaust emission standards.
In vehicles with a single oxygen sensor, the oxygen sensor is installed upstream of the oxidation catalytic converter.
In vehicles with two oxygen sensors, one oxygen sensor is installed upstream of the oxidation catalytic converter and the second is installed downstream of the oxidation catalytic converter. Both oxygen sensors are identical.
The function of the oxygen sensors can be assessed by evaluating the air ratios in different operating conditions.