I installed Skyview update 4.0.1 along with the wiring change from Vans.
Now the volume control on the SL40 has no effect; the volume stays on what I think is full. I also don't get the I (intercom) indication on the SL40 display.
Did you change any presets. If you went into the menus(on the SL-40) there is one that takes the volume adjustment from the knob. I changed it on accident once and had the same result.