O2 Sensors on 4.3 MPI - S1 vs S2

okubricko

New Member
Sep 13, 2022
6
Boat Info
2016 Sea Ray 21 SPX
Engines
4.3 Mercruiser MPI ECT
Hey all,

I have a fault, using Vessel View, that says I have an O2 sensor fault. It's at Port S1 (812-16). Is that the sensor on the top or the one farther back?

I guess I can just keep unplugging the O2 sensors until I narrow it down, but was hoping someone knew the difference between S1 and S2.

Thanks for the help!
 

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