Made a start on removing alarm, but first I tried starting truck, fired straight up, revved it, ran fine then started to splutter & loose power eventually dieing. Started a few times during the day but ran really rough only for short time before cutting out.
Found another interface linked to the windows, but if disconnected Windows don't work. ( see pic for wires !) Not sure what black wires should be connected to.
Alarm won't arm or do anything with fob either so over the next week or so will be disconecting it all, just need to know about those black wires.

Need to know where to reconnect the black wires
Thanks all

 

READ THIS CAREFULLY:

This wiring is a HUGE mess. Some amateur did a hack job on your wiring. Been a long time since I have seen wiring this chopped up.
And I have been doing car wiring for a few decades.
Nice electrical wiring Horror Show.
The wiring may not have anything to do with your engine fuel/spark problem, but it is a good place to start.
Because it WILL cause you other problems in the future, if not now.

First, get a factory wiring diagram, and strip out anything that is not OEM.
Start from a clean, OEM position. And do not screw up on reconnecting the wires, because that in itself will just add to the problem.
The ONLY proper way is to solder/heatshrink the connections. Use heatshrink with internal adhesive, to 1) waterproof connection, and 2) to keep heatshrink in place (you will have many wires splices beside each other).

BTW: the black wires look like lamp cord and are not OEM. And not for automotive use.
Your hint is that they have square jackets.
That in itself tells you something about the competence (not) of the original installer.
And fuses hanging off spade connectors? That just adds to the insults.

And you have something really bizarre going on. You have what appears to be 12GA wires connected to 16 or 18GA wires. And that is a huge red flag.
You also need a voltage probe with inductive pickup.
And you also will need a boatload of patience.
Chasing electrical gremlins can be the most difficult of vehicle repairs.

If you ever have to make fused links, instead of using a bunch of inline fuses, use a fuse terminal block and terminate the wires there (aka secondary aftermarket fuse block).
You should hardly ever need to do that, unless you are adding massive sound, offroad lighting, or other heavy draw accessories.

 

chevykev
What model year do you have .. ❓

The guys here are giving you good and sound advice and telling like it is 😮 being a Brit and more conservative, I tend not to.

Both hummerz and finall solutions are good, the point exposed wires will eventually corrode, and crimp connectors are just another thing to go wrong. Having said that about crimps, GM documentation describes using "Splice Crimp Tool J-38125" and "Duraseal Splice Sleeves" but it's a lot of faff.

Sealed wires and soldered joints are the way to go, all connections should have the same wire colours and matching wire sizes.

If you need wiring info, PM me, either here on FB, I have the complete set of OEM 04 wiring diagrams and related info, but it's too large to post. Failing that I have GM Service Info for all years, but it's no so easy to use.

Like I said, I'm not sure where you're located in the UK (think you're over here?) if you're not too far away I'm happy to come and assist.

 

Thanks, all good advice, it's definitely got to go, which I'll be doing over the next few weeks as I'm away for a couple of weekends.
oceanbrave, it's a 2003 & previous to me had sound system & games console in, ( wiring for current radio/cd is as bad ) also found today remains of laser scanner jammer ! I'm not that far from you, Burton on trent

 

That's not too far for me, so let me know if you would like some hands. I've got most things, heat guns, Weller soldering kit, Tech2, fine electrical tools etc electronics is my field.

 

Thanks a lot. I do alot of soldering at work, so got most kit, tech 2 might be handy though, only got a cheapy code reader which is only good for basic stuff. Like I said, busy for next couple of weekends so will keep you posted

 

 

Chevykev, just take your time, work on one circuit at a time as you complete the removal of that leg then test that function. As Finall mentioned you have a lot of non OEM (not even vehicle wire) in there that needs to be traced back and removed. Once you get to the splice point were they were added you should get to the original wiring which will be color coded and will be able to be identified and the source determined.

Don't get fustrated, we have all had issues like this in the past when someone has done things badly that need to be fixed. Keep at it you will get it fixed! There is a lot of resources on this site and many willing to help you along!

 

Do you sense that burnt wire smell?

 

Just another thought, should fuel flow from here with key on and pressing pin ? ( it doesn't) not had chance to do much else yet.