Dave,
If the harness was made by us (SteinAir), the d-sub connectors are crimp type. First, gain access to the wire side of the connector. Slip the white end of the pin extractor over the wire you want to remove and push it into the hole and over the pin. You should be able to feel it seat. Now pull the wire and extractor out as one. If it is stubborn, pull the extractor out, rotate it 90 degrees and try again.