I just bought an avic d3 that should come in a few days and I want to be prepared for my 2003 Silverado I bought the peswips steering control module and axxess gmos-04 integrated harness, does anyone have a heads up before I dig in, also I have read that you don't have to find the vss and reverse when using the gmos-04 is this true or does it not apply to my truck. Any info is appreciated. Thanks in advanced.

Have the in-dash install kit (the bracket that holds the radio and provides a trim cover)?

On my 07 the GMOS-02 kit had the VSS and reverse I think.

I've got the GMOS-01 for my 06 Impala SS and it's not getting/passing the VSS signal for some reason. It does, however, handle the reverse. I've also got the SWI-PS SWC module and it's a PITA. I may have gotten a bad one, but when I talked to PAC, they instructed me to wire in a small capacitor between a couple wires and even that did not help.

Search around for other threads about the GMC/Chevy 2500HD installs. There is a quirk or two that may apply to you regarding illumination hookup issues.

My dimmer doesn't work in my truck either, the install guys took my dash apart again after the first test and couldn't get the dimmer to work, so I told em f-it cause at that point I had been waiting 3 1/2 hours.

I have on 03 silvy too. The VSS wire is the green with white stripe behind your instrument cluster. My auto dimmer didnt work either so I had to tap into a wire over at the connector where the headlight switch is. I forget which wire though- I wanna say it was brown but I think there was 2 brown ones. I had to cut a little bit of plastic inside the dash near the bottom cause the bottom of the D3 was hitting it.