having just sorted out my SRS I can tell you yes polarity matters .. even though technically it doesnt I had the pretensioner code high resistence (after changing the ecu what a job)
the pre tensioner is the blue plug the airbag the yellow plug I did them with bullet connectors so I can a) remove the seat b) switch the polarity easily
the sensor is under the carpet (green or orange type) on the rail just forward of the rear seat mounts for the green type on the inner cill for the orange type
looking at your codes you need to do away with both under seat plugs asnd get another side impact sensor to test it
it only took me 2 days of head scratching and the interioor out to fix mine
to save confusion on the pre tensioner and the side airbag I put the female connectors one side and males the other and vise versa on the other plug that way they cannot be crossed over (if you plug the pretensioner into the airbag wiring and you get a fault it will point you to the wrong component )
so airbag side both femle on the car side both male on the airbag .. so polarity can be switched .. and the opposite on the pretensioner
dont forget to clear your codes when you make any changes to check .. I made that mistake thinking they would auto clear and re did wiring twice
