So I followed the instructions on LT1swap.com for my full wire harness including underhood fuse box install. This is a 2005 5.3 truck flex fuel motor. I made sure I had all of the fuses and relays in place, and then hooked up a battery. None of the 3 extra wires first, just power to the wiring that came with the engine. I checked the block at C1-B11, no power at all. I got curious, so I sent power to my truck (the other fuse block, etc). I then turn the key to "run". I check, and C1-A9 has power, so that one checks out. I then check C3-F1 (the tank relay) and nothing, no power. I get past that by finding switched power on C1-A11. I also have no wire on C100-pin3, there just is no wire there at all, never was, it has a factory plug in it. So I switch the key to start after hooking up the two switched power points. I have power at my tank, nice pump action, but nothing else, the engine doesn't even seem to try to turn over.

Anyone have a clue?

Orlando

 

those instructions are for 2000 model year specific fuse block..changes took place almost each year.

 

Is there anywhere I can find the specific instructions for the 2005 fuse block? I have the xls download file from that year, but it doesn't include C1, C3, or C4, just C2 and C100, C152, C153...

Orlando

 

What did you find out with your 05 Fuse Block?

 

these are 2005 schematics of fuse block.

from top left to bottom right.

B+ Bar 1 of 2
B+ Bar 2 of 2
BTSI, B-U LP, O2A, O2B, SEO IGN, TBC IGN 1 and TRL B-U Fuses
Ign 0, RR WPR, SEO ACCY, TBC ACCY, TBC IGN 0 and WS WPR Fuses
Ign 1 Relay Bus -- 1 of 2 -- ETC, ECM, PCM I, SBA Fuses, Inj 1, Inj 2 Fuses
Ign 3 Fuse 1 of 2
Ign 3 Fuse 2 of 2 -- ult
Ign E and SIR Fuses
Ign Switch -- Accy-Run and Run-Start Busses, and IGN B Fuse
Ign Switch -- Accy-Run-Start, Run and Start Busses, IGN A, and CRANK Fuses

Thing to remember, the under hood fuse block DOES NOT provide power to everything needed for engine to run. Some things were powered by the IP fuse block, under the dash of the original vehicle. So You have to wire these up separately.

this includes:

OXYGEN SENSOR HEATER CIRCUITS, see BTSI, B-U LP, O2A, O2B, SEO IGN, TBC IGN 1 and TRL B-U Fuses, power comes from IP fuse block.

PCM and TRANSMISSION SOLENOIDS, see Ign 0, RR WPR, SEO ACCY, TBC ACCY, TBC IGN 0 and WS WPR Fuses, power flows FROM IP fuse block, into Underhood fuse block, then right back out, this is circuit 1020.

good luck. I usually prefer to do away with the under hood fuse block, and build my own smaller fuse block.

 

and it only lets 10 attachments at a time..so here is the last one

this picture is:

Starting Schematic

 

Any chance you could email these to me? bowtie_or_nothin@yahoo.com Taking for ever for me to open them.

Might as well post this here since its of the same topic. Got my 05 fuse block all wired up, truck runs fine, but shifting is another issue. I'm at the point of pulling the 13 pin off of the side and running a key switched wire to it. But reading what you said, sounds like I have more key switched wires to power up. They have to run through one of the two plugs under the fuse block... but what ones?

 

sounds like you have not powered up circuit 1020.

A fuse in the instrument panel fuse block provides power to the underhood fuse block via C1 pin C9. This circuit simply jumps over to another pin on the C2 connector pin E11 of the underhood fuse block. You should find 2 pink wires at that location of C2 E11 on the engine harness. 1 wire feeds to PCM blue connector pin 75, the other feeds to the transmission, power for solenoids.

I guess pin 75 of PCM is not needed for PCM to run, as if you look at F-Body schematics in the 99-02 range, they did not have a pink wire here, as trucks did. So this should explain your trans shifting issues.

 

So if I supply fused key switch power to C1 pin C9, I'll be in business?

 

Yes, you should be getting power to your trans then.