1990 C1500 stock ECU, can it be removed when going with a stand alone harness?

[Big-Sexy907]

Working on my swap and thought there would be enough room for the factory ECU and the LS to reside in the same location. After taking the dash apart I noticed that there isn't, and if I replace the 90 ECU with the swap ECU it should fit.

Now, does the factory ECU even need to be left in the vehicle? Or can I remove the harness and its related components in favor of the new standalone harness?

I'm using a 4l80e with a Nelson harness.

[Chevy-Art]

There is no need for the 1990 ecm, so you can remove it.

[Big-Sexy907]

Thanks Art! I'm going to look at removing the passenger side bulkhead as well.

[vortecyota]

Chevy Art is right, also there's no need to put the LS1 PCM in the cab unless you just desire it to be hidden. Personally, I don't mind them being visible but I know everyone's taste differs. Good luck and post pics!

[Big-Sexy907]

Thanks for the information fellas, I'm going to remove the harness from that side of the firewall as well.

Does anyone know what wires go through that portion of the firewall, or is that just PCM control for the engine only?

[Chevy-Art]

Some of the cluster wires and harness for the old ecm go through there.

[Big-Sexy907]

Some of the cluster wires and harness for the old ecm go through there.

From what it looks like the VSS wire and the fuel pump relay are the only two wires needed through that bulkhead, there is also a larger (10 ga) power wire that goes through there as well for the dash power I think. Anyone know of any other wires that go through there?

Better yet, anyone have a diagram that shows the wiring of the dash, and it's colors?

[GreyChevy]

Diagram would help me out as well