This is more of a FYI thread - I recently had an 06 LS2 3LT in the shop that was acting really weird. The reason the car came in was because it would run poorly and die as soon as you took the car out of park. This started happening as soon as the car was taken out of storage for the winter.
When the car came in it had the following codes:
P2455
U1000
U1017
U1040
U1088
U1193
U1153
U1024
U1064
B1327
B2375
B2355
B1420
When I first got to the car I started it up and drove it around the block without an issue - at first I figured I just needed to check out the battery. So I took a look and it was only about 3 years old and my sine wave tester showed it was right around 650 CCA. I put my smart charger on it and let it top the battery off. I cleared the codes and went to take it for a ride and as soon as I put it in reverse it sputtered and died.
First thing I did was check the fuel pressure - it was right around 60 psi and it never moved even after I put it in gear and it would die, hooked up my HEI spark tester and there was plenty of spark - it actually sparked once after the car died, checked the #1 fuel injector with a noid light and it seemed like it was pulsing ok. I thought maybe the tune somehow got corrupted so I used my EFI live and took a look at it - then flashed in the newest OS. After the tune it started and kept running when I put it in gear - so I took it for a 20 minute drive, everything seemed fine, until I put the car in park - the gauges all swept, pretty much all warnings went off, Sevice Active Handling, Service ABS, Service Engine Soon.
After that I re-checked the codes and this is what I got:
P0700
U0073
U2100
U2108
U2106
U2105
U2100
The P0700 and the P2544 were pointing toward a bad TCM and there is a TSB out about wiring pulling out of the connector at the transmission plug, so I put the car on the hoist, checked the wiring at the plug, along with all of the visible grounds - and looked at all of the wiring looms - especially the ones under the hood, but everything looked good (the car has a little over 20k miles on it). So since it seemed like the ECM re-flash made a positive improvement I read and re-flashed the TCM. There was no change in the cars behavior - in fact it pretty much reverted back to the symptoms before the ECM re-flash. After thinking about things a little longer all of the U1000 codes then all of the U2100 codes had me leaning toward an issue with the BCM. The BCM is the gateway between the Class 2 data line (all of the U1000 codes) and the GMLAN data line (all of the U2100 codes) - to verify that there was an issue on one of the data lines I used an oscilloscope to watch the sine waves - but I found nothing on any of those lines. At this point I'm back to square one.

I unplugged the ECM, cleaned the connectors and plugged it back it - looked things over best I could for issues with the harness, same with the BCM and TCM. The car actually ran pretty well after that, I took it on two drives and everything seemed like it was ok. I leave to go on a 40 minute drive and fortunately for me the car acted up 2 miles from the shop.

This time it wouldn't just die - it was trying to run but it seemed really confused, sputtering and surging - not happy at all. I nursed it back to the shop and verified fuel pressure again - I also check for fuel flow, they both seemed fine. The only other thing that could be effecting the fueling is the injector drivers in the ECM.

So I installed a new ECM - relearned the security system, did the crank relearn and the car hasn't acted up since.

I'm just hoping this helps someone in the future - it was a pain to diagnose but it's back to normal now.

 

Thanks for posting and nice work!!