ALT hook up , and Power to relay help
 

Old 5.7 Alt. wires.... brown and red ( Red spiced off big terminal on Alt) ... new to me 2001 5.3 LS .... Alt has 2 wires brown and gray......should I splice the wires from the old plug into the LS ....is red the same as the gray wire......I also used the Hei pink wire to power the relays, is this correct, or should I run it back to pink wire from key switch.....using Aaw classic update harness...... Engine cranks no power to the fuel pump as far as I can tell.....Thanks....Ed

Re: ALT hook up , and Power to relay help
 

You don't have to splice anything on the alternator. The small wires go from the alternator straight to the PCM, nothing needs to be done with them. You will need the big red wire hooked to the battery though. Depending on how how did your wires, you may need to add the wire that goes to the firewall bulkhead that powers up the fusebox under the dash.

As for the relays, I assume you mean the main ignition relay, the one that powers up the LS harness, it will be hooked to the HEI wire, but only to turn the relay on, not powered up by it. It will need a constant power to power the relay.

Re: ALT hook up , and Power to relay help
 

Thanks Eric, I do have the big red wire hooked up, and have power to the fuse box in cab. Pink Hei wire hooked to the relays....and red power wire from relays to junction post, and to battery. I will double check ground wire and fuel pump power. And make sure I have a spark....Thanks Again.

Re: ALT hook up , and Power to relay help
 

Checked for power at the relay, no problem....then to the ground.....touched the negitive battery cable to the fuel pump feed. Fuel pump kicked on. I have no idea what wire I used from ecm for a ground, going to add a ground and hope that back feeds anything else that needs it.

Re: ALT hook up , and Power to relay help
 

The fuel pump isn't grounded through the PCM, its grounded separately, usually near the tank. Or are you talking about the ground for the relay?

Re: ALT hook up , and Power to relay help
 

Ground for the relay!....I must have messed up on my relays some how, if I jump from battery ground to the relay ground jumper the tester lights up and pump comes on....2 seconds and the test light goes from bright to dim. I have cycled the pump about 10 times, the engine should have enough fuel, but won't start. Tank and pump in tank are grounded.

Re: ALT hook up , and Power to relay help
 

I just fired off my LS swap and have similar question on alternator wiring. Plug on PSI harness didn't match alt on 2006 escalade 6.0. Colors on 2 small wires don't match. I've fired it off and everything seems to be working just fine without wires connected. Battery is getting charged and volf meter is working. I don't want to screw something up, so just leave it?

Re: ALT hook up , and Power to relay help
 

It sounds like you did miss a ground somewhere. If you modified your own harness, then I would just double check everything. You would have had to add the ground for the fuel pump relay, usually by tying it into the grounds already in the harness, but if you didn't do that, then you will need to add one, just make sure its a good ground! As for the no start, could also be the same problem if you did in fact hook the fuel pump relay ground into the grounds in the harness, but missed hooking the ground up when you installed the harness on the engine. There are usually three grounds, one at the back of each head, and one down low behind the power steering pump, miss that one and it won't start, seen that happen a lot.

Re: ALT hook up , and Power to relay help
 

On a 2006 engine the alternator is controlled by the GBCM, (Generator Battery Control Module) if you don't have that, the alternator will default to about 60% duty cycle or 13.8v or so, that's why it's charging. What year harness did you order? Never used an aftermarket harness, but it may be that they set them up for an older alternator that is controlled by the PCM, but it would require the PCM to be set up for it. There are other ways around it, but they can be a bit complex, so using an older alternator is usually the easier option.

Re: ALT hook up , and Power to relay help
 

As always Thanks for the follow up. I redid my own harness, 2001 LM7.....I tried to use grounds in the harness. I will look at the engine grounds and try again....no after market harness...mine is a DBW. has tac module and electric pedal. Branden did the reflash.

Re: ALT hook up , and Power to relay help
 

Ls1nova71, thanks for response. There’s a local alt shop that I’ll check with to make sure everything is wired and working correctly.

Re: ALT hook up , and Power to relay help
 

Some progress, ground issue solved.....fuel pump ground on frame clean with star washer stainless bolt.....not good enough....extended the fuel pump ground to the relay ground.....that works.....cycled the switch about 10 times pump runs no fuel yet.....will try adding another 5 gallons of gas. The 3 engine grounds all seem to be good... Thanks for the help.