I bought a 2002 s10 crew cab LS 4x4 for a little beat around truck, got it cheap, but the wiring harness’s had been cut and spliced, no issues other than the o2 sensor harness was cut off about where the last sensor is before it rides along the frame on passenger side, found what I think is it under the computer but not sure, looking for any help on this, throwing a o2 sensor code and also a P0300 multiple misfire code

 

The O2 sensor isn't causing the misfire.

 

Go to a junk yard and get the plug from another S10 and splice it into the wires that you have. Do a tuneup on it and that will probably fix the misfire.