LS3 Wiring Issues

[mbisett]

I am in the middle of running the Ron Francis chassis harness and the Blueprint LS3 ECU harness - and boy I am in way over my head. Here are some of the issues/questions I have:

1.Where in the cab can you mount the rather large fuse panel block from the ECU harness? Everything is already so tight on the firewall there is no more room for this block.

2. What and where does the ECU "Bulkhead" leg go - it is not in the wiring diagram I am using so I am curious if it is even needed. It apparently can be used for:
GMLAN communication link; Tachometer Signal; vehicle speed; MAP; oil pressure gauge, etc. "if desired". It has many other outputs but I am not sure any of these are required to make the engine run as a cruiser. Your thoughts would be appreciated.

3. Since the ECU harness has most of all of the engine sensors connected to it, do I even need to use the RF "Sending Units" harness?

TIA

[edwardb]

I am in the middle of running the Ron Francis chassis harness and the Blueprint LS3 ECU harness - and boy I am in way over my head. Here are some of the issues/questions I have:

1.Where in the cab can you mount the rather large fuse panel block from the ECU harness? Everything is already so tight on the firewall there is no more room for this block.

2. What and where does the ECU "Bulkhead" leg go - it is not in the wiring diagram I am using so I am curious if it is even needed. It apparently can be used for:
GMLAN communication link; Tachometer Signal; vehicle speed; MAP; oil pressure gauge, etc. "if desired". It has many other outputs but I am not sure any of these are required to make the engine run as a cruiser. Your thoughts would be appreciated.

3. Since the ECU harness has most of all of the engine sensors connected to it, do I even need to use the RF "Sending Units" harness?

TIA

I put the LS3 fuse box and PCM in the cab for my 35 hot rod truck build. Agree not really space on the firewall side. Are you using the GM Performance electronics package? I found their instructions were decent. Explained what was needed and what is optional. Agree you may not need the RF sending unit harness. I de-loomed most of that harness and routed per my wiring installation. Lots of pictures and explanations in my build thread linked in my sig line below.

[mbisett]

I am using the GM Performance Package. Since I am a real novice electrical guy, I am using the instructions as best I can but not sure what is optional. I would rather use wiring diagrams but still having difficulty determining which is optional on open ended harness connections (i.e. Bulkhead). I will revisit your build thread some more - it is a fantastic tool. Where did you end up mounting the PCM fuse box?

Thanks Paul!

[Its Bruce]

See information on the bulkhead in the following link (bulleted list toward bottom of the post): https://thefactoryfiveforum.com/showthread.php?46750-LSx-Engine-T56-Magnum-in-a-Roadster&p=532415&viewfull=1#post532415

If you don't plan to use any of those items, you don't need the bulkhead. I suspect you'll at least need the tach?

As a warning, I have heard issues with NOT having the VSS wired up. For whatever reason, the GMPP ECU may want to see a vehicle speed. Unfortunately, it required an additional pin/wire in the ECU that isn't provided by GM. I can help more if you need to walk through it.