Quote Originally Posted by hotrod View Post
1. If i've been reading right the only thing I keep from the old harness would be oil pressure and water pressure and a/c?

2. Since my sierra has the moonie style gauges, how does the speedometer get wired in for the new harness to control the speedometer that's in my truck now?

3. The ses light, does the new harness get spliced in to the wire coming from the sierra pcm? I don't think I really found a definite answer on that from reading around online. Could someone explain how to use the ses light that's already in the dash?
1. What you need from the old harness are the wires that go to you gauge cluster. They are oil pressure, and water temperature. For the water temp I drilled and tapped the water pump, probably not the best way but it worked for me. I think I used the LS1 sending unit for oil pressure.

2. For the speedometer to work I used the wires what come from the VSS on the transmission, they disconnect from the rear of the trans and go into the cab. The colors are HI 400 Yellow and LOW 401 Purple.

3. For the SES/CEL, you are going to have to tap it into the corresponding wire that comes from the donor vehicle PCM. And you are also going to need an ALDL/OBD II connector from a 96 or newer GM car or truck.