Error code 203 (O2 system)

[Rob2021]

Hi everyone, I have a 2015 Yamaha 212ss (California model) and I have the error code 203 (O2 system) on both of my engines. Since my boat is a California model, it has catalytic converters. Does anyone know exactly what this warning is for ("O2 system" is not very specific)? I read in another thread that it was a warning for O2 sensors but I know that there are two sets of O2 sensors on the California model boats (one pre cat and one post cat). Any help I could get is greatly appreciated!

 

[212s]

Can't help with which one, but yes, sounds like oxygen sensors.

 

[Rob2021]

Does anyone know if the pre and post cat o2 sensors are the same? I’m looking on Yamaha part diagrams and I can only find one sensor labeled as an o2 sensor so I’m confused.

 

[tdonoughue]

My guess from some internet research is that they are different.

The O2 sensor (that Yamaha calls an O2 sensor) seems to have a different part number and description from the sensor after the cat, which they call a 'thermosensor assy' (but folks on the web call it an O2 sensor, too). So I am betting they are different.

 

[Rob2021]

My guess from some internet research is that they are different.

The O2 sensor (that Yamaha calls an O2 sensor) seems to have a different part number and description from the sensor after the cat, which they call a 'thermosensor assy' (but folks on the web call it an O2 sensor, too). So I am betting they are different.

Thank you for your input. I was almost fully sold on them being the same but I am planning on removing the sensors from my engine and comparing them anyway. I will post my findings as soon as possible.

 

[TreeRX]

Thank you for your input. I was almost fully sold on them being the same but I am planning on removing the sensors from my engine and comparing them anyway. I will post my findings as soon as possible.

Are the o2 sensors the same (pre vs post cat)? Also do you know what size o2 socket I need? I also have the California motors with fault code 207, and need to replace one of the sensors, but don't know which one.

 

[Rob2021]

Are the o2 sensors the same (pre vs post cat)? Also do you know what size o2 socket I need? I also have the California motors with fault code 207, and need to replace one of the sensors, but don't know which one.

I’m really sorry but I am not completely sure if the sensors (pre and post cat) are the same. I am pretty sure I remember them being the same but if you want to check them just swap the sensors and see if the warning changes. Also I’m not sure what size socket is needed.