What ECU are you using? If your using the JDM PR3/PW0 here's, the pinouts.
http://tech2.hybridgarage.com/ecu.php?ecutype=pr3_a
It says B19 is your knock sensor, so maybe you just haven't wired it up (your stock B18A wouldn't have one). I can't promise that info's right, but that website is pretty reliable for information.
If your using an OBD I ECU with a conversion harness, the knock sensor is D3.
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Andy - Reinstated
Hybrid Forum Moderator
'06 Subaru Legacy Spec B - Stock, for now
'98 Civic EX - CTR headlights and grill, Kosei K1's, for sale
'90 240SX - SR20DET that will never get installed, project car.