What does it mean?
Modern vehicles use both an upstream and downstream oxygen sensor. The upstream oxygen sensor (O2S) is located ahead of the catalytic converter. It is used to determine the concentration of oxygen in the exhaust gas. This information is used by the PCM to control the engine air/fuel mixture. The sensor compares amount of oxygen in the exhaust to the surrounding air (there is an opening in the sensor that is exposed to the atmosphere).
It generates a corresponding voltage which is transmitted to the PCM. The PCM then controls injector pulse based on this value. The downstream oxygen sensor is located behind the catalytic converter and is used to check converter efficiency. It does so by checking the oxygen content of the exhaust after it leaves the converter. For this reason, downstream O2 sensors are known as catalyst monitors. Modern vehicles use heated oxygen sensors (HO2S).
These sensors contain a heating element that brings the sensor to operating temperature faster. This allows the PCM to use the signals input sooner, for more precise fuel control and reduced emissions. The heater circuit is energized through a relay that closes when the engine is cranked. The PCM monitors the heater circuit and will turn on the check engine light if it finds a problem. The code P0041 stands for O2 signals swapped bank 1 sensor 2/bank 2 sensor 2.
This is an unusual code; it doesn’t come up often. It indicates that the oxygen sensor signals have been swapped. It is similar to P0040, which stands for O2 sensor signals swapped, bank 1 sensor 1/bank 2 sensor 1. The only difference in these codes is the location of the sensors. The same diagnostic strategies can be uses for both codes. It is typically Ford vehicles that support these codes. O2 sensor locations