There are a million and one options for an engine harness for your LS swap. Most of them are as simple as plug and play and a few wire hookup. While these are all great options, I chose to do things the hard way and build my own harness. The reason for this is because I can not stand harnesses that have pigtails too long with excessive wire or wires too short. I prefer a harness that tucks in nicely and is semi-hidden. Also most of them use split wire loom and non-terminated wire ends. The biggest reason is because I am not using the stock PCM. With my MS3x, there is no pre-made harness, and if it was it would still have the issues I listed earlier. So I ordered almost all the engine sensor connectors from EFIconnection.com , they are great to deal with and have almost any connector you would ever need.
The first part of the harness I started building was the fuel injector harness. Making sure the wire length was just right so the harness would lay down flat as possible.
Every connector on the harness is labeled using printed heat shrink labels.
You can see how the harness stays nice and tucked, but has enough slack to not be drawn tight.
MAP, IAC, TPS and IAT sensors wired up, again every connection labeled.
No excess wires here.
The Dome pressure sensor used for boost control.
Cooling system pressure sensor, used to datalog cooling system pressure as a telltale of head gasket sealing issues.
Holley 120psi fuel pressure sensor.
Cooling system pressure sensor wired up.
Bank 2 ignition coils wired up and plug wires made.
Bank 1 ignition coils wired up also
Once all the individual harnesses were terminated and trimmed. They were zip tied into place to ensure proper positioning.
Then came pinning the Maven Performance 47 pin bulkhead.
Once that was done, the boot was pulled up over the back of the shell and the heat shrink was shrunk to ensure a clean look.
The first harness in place and plugged into the matching bulkhead. I will be able to unhook the entire engine harness with two plugs.
I also installed the dual Spartan 2 wideband oxygen sensors and controllers. The controllers are sealed weather tight and therefore can be mounted outside of the cab. In this instant they are mounted right next to the 4l80e transmission.