Solved.
If anyone is Interested:
PAC SWI-RC works well with a pioneer unit. I used red, black and white wires from the PAC unit and attached them in this manner - Red from PAC to red 12 volt switched on pioneer unit. Mine had 2 black wires from the PAC so I attached one to black ground wire from pioneer harness and the other to the black wire from the OEM harness ( the one that went into the OEM headunit). The white wire from PAC went straight into the solid Blue wire on the OEM harness that went into the OEM unit.
Then you can go ahead and program as listed on the PAC website.
Cheers!
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