90 sierra rcsb ls swap

[Chevy-Art]

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.

[hotrod]

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.

Thanks man, that clears up the wiring i was wondering about.

You wouldn't happen to know what color wire the ses wire would be would you? Not sure if the wire colors vary from different years.

[Silverado889]

http://www.lt1swap.com

This website has tons of wiring info on it. It has all the pcm pinouts for all the years. And dont forget that the pcm shows ground for the SES light, not 12v.

[Chevy-Art]

Forgot to mention nice looking engine and trans you got. Where did you buy it, local to you?

[hotrod]

Forgot to mention nice looking engine and trans you got. Where did you buy it, local to you?

It wasn't local, it was at the salvage yard, just had to drive about 35 miles to get it, which isn't far. I figured since you lived in san antonio there was tons of salvage yards in your area.

I was planning on getting a motor from ebay, then started adding in shipping and decided it would be cheaper to look at a salvage yard.

[hotrod]

http://www.lt1swap.com

This website has tons of wiring info on it. It has all the pcm pinouts for all the years. And dont forget that the pcm shows ground for the SES light, not 12v.

Thanks, that's where i've been getting all my wiring info for my stand alone harness.