Any GTO experts out there?

Holy smokes that is a wealth of information! Thank you so much. His keyfob which is actually part of the key on these does not work. It never worked since he got it. When he had it at the transmission shop they took it apart to replace the battery which is not an easy task for these and then now he is starting to have these weird issues so I am beginning to think that may be the culprit. Its weird, he drove it sparingly before having the transmission rebuilt and now this mysterious no crank issue cropped up. I think the taking apart the keyfob is a clue, but my son is not convinced. I told him to order a new one but they are spendy and he doesnt make that much money.

They are discontinued from GM and says the batteries are not serviceable.

There are some to be found. There are videos on how to replace the battery but it requires soldering which he and I are not that comfortable with doing. I guess we cannot make it worse.

See if one of those local phone battery shops can replace the battery for a fee? Thye might be more capable with the tiny soldering iron.

Good idea KPE. Might give that a shot. Typically no soldering is involved, but the geniuses at holden found it necessary.

I would think about a subscription at alldatadiy.com
I think it is about $25 for a month per vehicle but you will have access to the factory service manual plus any Technical Service Bulletins. The service manual should have troubleshooting charts for no crank issues along with the wiring diagrams.
I had a subscription when I had issues with my 96 Chevy K1500 and with my old Sunfire

This site has links to 2004-2006 GTO service manuals, https://markquitterracing.com/freeservicemanual/

There is even some mention about wiring issues with the BCM https://markquitterracing.com/bcm-wiring-harness-repair/#:~:text=On%20the%202004%2D2006%20Pontiac,the%20passenger%20side%20glove%20box.

ITS ALIVE! So my little prick son just kidding had it into the shop where he works for a deep dive. Found out the dude who owned it 2 owners ago rewired to the starter because he apparently had some issues. Thankfully this took 30 minutes to figure out so the poor kid isn’t out a ton of money. Anyway, they rewired it and the key turn the ignition straight forward will fire up the fuel pump. He then pushes a button that they installed that is a direct wire to the starter which is fed once it is fed 12 volts. Starts right up everytime! I’m guessing the gauge wire that dude used was suspect or he had crimps or poor connections. My son showed up today at my house with it and was revving it up. Turned it off started right up. Did this like 5 times in the driveway. I said that’s great it’s cold out. Well the little bugger had it fixed already and had it at work the hottest day of the year Thursday and it started fine that night. I’m so happy for him! Now he can enjoy it but I’m going to surprise him with getting the 86 Fiero GT he has clutch figured out so that is running good. I arranged this Friday unknowingly to me that his GTO was fixed. Well once the fiero is running then he will either sign it over to me or sell it. We will see LOL

My son got new tires on the GTO a couple weeks ago and has been enjoying the heck out of it.
As a surprise to him I went to the transmission shop where his 1986 fiero GT has been sitting for nearly a year and had them get the clutch fixed. I picked it up last night. It ran really rough at first and died several times before I tried leaving, but once I got moving it actually drove really nice. The brakes are shot so that made it interesting drive home. Plus there is no rearview mirror and I couldnt adjust the outside mirrors. To top it off it started to rain a bit so I turned on the wipers and they disintegrated and flew over the car LOL.
Then I get to the parking lot where he was going to meet me for a package I said he had delivered to our house that looked “important” (which at the time I told him that it wasnt, but one came yesterday just in time LOL) I tried to back into the parking space but couldnt find reverse LOL.
(Later figured that out last night) He was really surprised. It will be a work in progress and he was so relieved because I knew he had basically just given up on it and he actually said it last night.
They had to send off the flywheel to be machined because the clutch essentially disintegrated inside there. Shifts really nice and is a riot to drive.
Well, all my pulltab winnings came in handy time to replenish.

Well end of a journey for my son and the GTO. He sent it down the road last weekend. He ended up coming out about even on it after everything which I think is fantastic. It was a fun car, he just wasnt driving it mainly because of that rhino lining was about to make the bumpers fall off because of the weight breaking the plastic clips so it was time to just move on. I also sold the Fiero last Spring so he is down to 1 car his Chevy Bolt EV which he loves. What a lifestyle change LOL