1. when turning ign switch on or ACC that the dash goes dark, does it still do that ?
2. That you also had a U1000 comm DTC, that would be the slow speed class2 network which is 1 wire per controller
3. That Tech-2 connects to all controllers, except PCM, BCM, ABS (EBTCM) have you in fact able to connect to all other controllers such as doors, seats, IPC (dash), HVAC, Radio, etc ?
You must know by Tech-II if and what controllers can be connected to by the network
Spend time on this a to the class 2 network wiring
Goes back to testing at the splice packs, in this case SP205 and 208, you see below it says where they are located
This would affect the ign switch as it needs to send data over class 2 (CAN) network
This shows at what position of splice pack and pins of each controller
You need to load test that battery, cannot tell by voltage level alone
Also, there was a problem with the battery cable lugs and GM had to replace one of them
cannot recall if it was the positive or negative.
Check battery ground cable to frame is tight and wiggle those lugs to battery posts for firm connections
Also, the end of positive cable to fuse box.
With a D/C voltage meter, watch voltage at battery when someone turns the ign switch on, or start or in ACC
Also try a test with a battery charger hooked to battery posts and see if any changes that way
I did some more cleaning and used an electrical liquid. On the pcm, fuse box connectors under hood on right side and the connector for the abs unit.
Put it all together and put the ignition on. Then all of a sudden the fuel gauge showed that the car had gas. So I tried to start and boom there it is. No problems and the car started perfectly.
I run a diagnostic test and some codes accured. But as you said I think they will dissapear after a ride.
So once again!
I am grateful for your expertise and help.
Thanks you so much.
If you ever plan to visit Norway let me know👍🙏
Being your Z06 has been parked for long periods, it would be wise to run some fuel cleaner in gas tank and also fuel injector cleaner and with OBD-II scanner or Tech-II to see what the long and short term fuel trims look like as being too lean or rich and if reporting any engine knock or misfires